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Pelican Technical Article:

Boxster Intermediate Shaft Bearing Replacement and Upgrade (IMS)

Time:

2 hrs

Tab:

$150 to $600

Talent:

*****

Tools:

Installation tool (included with the kit)

Applicable Models:

 
Porsche 986 Boxster (1997-04)
Porsche 986 Boxster S (2000-04)
Porsche 987 Boxster (2005-12)
Porsche 987 Boxster S (2005-12)
Porsche 987 Cayman (2007-12)
Porsche 987 Cayman S (2006-12)
Porsche 996 Carrera models (1999-05)
Porsche 997 Carrera models (2005-12)

Parts Required:

IMS Bearing Replacement Kit

Hot Tip:

Perform this upgrade when doing a clutch job

Performance Gain:

Years of reliable running

Complementary Modification:

Clutch replacement
101 Performance Projects for Your Porsche Boxster

This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.

Check out some other projects from the book:

Introduction

The M96/M97 Boxster engine has had a checkered past when it comes to reliability (see Pelican Technical Article: Common Engine Problems and Failures). One of the weaknesses identified in recent years by Porsche has been the intermediate shaft bearing (IMS bearing), which supports the intermediate shaft on the flywheel end of the motor (see Figure 2, Figure 3, and Figure 4). Porsche designed these motors using a sealed ball bearing that is pressed into the intermediate shaft (Figure 6). These types of bearings are typically used in things like copy machines and other machinery used in dry conditions. In theory, the area where Porsche designed the bearing to sit is supposed to be dry. However, after years of use within the engine, it would appear that oil and contaminants from the engine seep past the bearing seal, wash out the original lubricant and become trapped inside. The result is that the bearing now operates in a less-than-ideal environment and begins to wear prematurely. When the bearing wears out, the timing chains on the engine may disengage, and the engine will quickly self-destruct. When the bearing does begin to deteriorate, foreign object debris from the bearing circulates throughout the engine, causing damage to other areas in the engine. This appears to be one of the most common failure mechanisms present with the Boxster and 996 Carrera engine.

The center bolt that holds the entire assembly can also fail. If this bolt breaks, it will immediately allow the intermediate shaft to float, and the engine will skip timing. This will result in the complete destruction of the engine in a very short period of time (seconds). Typically, a deteriorating intermediate shaft bearing will also cause the center stud to weaken and break. The stud has a groove cut into it axially to allow for a sealing o-ring to seal to the outer cover. This groove causes a stress concentration to occur (see Figure 8) and promotes the failure of the stud. The solution is to pull out the bearing and replace the stud with a new one that is stronger and manufactured without any grooves (see a comparison of the old and new studs in Figure 7).

So how do you know if you have a problem? There are several warning signs. When you first start your car, you may hear a loud rattling noise that goes away after about 10 seconds or so. When you accelerate, you may also hear this noise too. This noise is the sound of the chains or the bearing rattling around in the engine because the bearing has deteriorated: the engine is soon on its way to skipping a tooth on the sprocket and costing you thousands of dollars. To detect the early stages of a failure, listen for a sound that is similar to what a throw-out bearing, water pump, or a belt idler pulley sounds like when the ball bearings begin to fail. If you have the car up in the air and running, you can listen carefully and you should be able to isolate the noise to the area of the IMS bearing (bottom rear of the engine, near where it mounts to the transmission), especially if you use a diagnostic stethoscope.

Signs of a failing IMS bearing can also be found by inspecting the oil filter. Shiny metallic debris from the balls used within the bearing itself may travel through the oil system and become trapped in the oil filter as well as small bits of black plastic from the seal on the bearing (see Figure 50 and Figure 51). During a routine clutch job, you can also simply remove the IMS cover and take a closer look at the bearing itself (lock and check the camshafts prior to removing the cover though: see instructions below). If the center shaft is wobbly, or the center of the bearing doesn't spin freely, then it's probably on its way to failure.

Another way to check the engine is with the factory PST-2 tool, or the Durametric tool (see Pelican Technical Article: Reading Fuel Injection Fault Codes / Diagnosing Problems). You can compare the deviations in the timing between the two camshafts to see if they vary widely, particularly when revving the engine (see Figure 18). Sometimes a failing IMS bearing will also trigger a "check engine light" warning on your dash, as the car's computer realizes that there is a significant deviation between the two camshaft readings.

What does a Bearing Failure Look Like?

My good friends at Callas Rennsport gave me a ring one day to let me know that someone had a 1999 996 convertible with 31,000 miles on it that had a bad engine knock. Knowing that I was writing a book on the subject, I called the owner up and took a look at his car. This was about a year or so ago (2009), and there were no options available to the general public to replace the intermediate shaft bearing. The owner of the car was quoted about $20K to replace the engine with a factory rebuilt one from Porsche. With only 31,000 miles, you'd think that the engine would last longer. It is important to note that the 3.4L M96 engine in this car is almost identical to the ones installed in the Boxster.

Speaking on that point, I did purchase the car from the fellow, on the gamble that the problem was with the intermediate shaft bearing. I knew that prototype retrofits were being tested, and that there was a pretty good chance that we would be able to repair the engine. Even if the engine was toast, then it would be a good excuse to write an article on rebuilding the engine!

Well, as luck would have it, I pulled out the intermediate shaft bearing cover and found that the bearing had completely disintegrated and there wasn't much left (which is what I actually wanted to find). This engine was running, and the car was driving, but every few seconds it would make a horrible screeching noise. Sometimes it would run for quite a few minutes with no sound at all. Hard to believe considering that the bearing was completely destroyed (see Figure 47 and Figure 48). I pulled out the bearing and found more bearing debris inside the intermediate shaft (Figure 49).

Seeing how a lot of the bearing was actually missing, I went on a treasure hunt within the engine, beginning first with the oil filter. The filter was quite contaminated with bits and pieces of bearing (Figure 50 and Figure 51). Seeing the debris inside of the filter, it became obvious that the bottom sump should be removed and inspected (see Figure 52, Figure 53, Figure 54, and the sump pickup in Figure 55). Curiously enough, this very low mileage car had previously had its bottom sump removed. I'm not sure why that would happen with such a low mileage car (perhaps it got scraped on something along the way?). I also noticed when I pulled the bearing that the intermediate shaft cover was one with an updated-style seal, which meant that someone had been in there and changed it out (probably because it was leaking at one time). Needless to say, there were a lot more signs of "meddling" than I would normally have expected to see on a car with only 31,000 miles.

So what can you do with an engine that has had this much bearing damage? The engine was still running when I took the bearing out, so I know there didn't appear to be any damage to the cylinder heads from the timing chains being out of sync. The oil filter appeared to do its job of blocking most of the bearing debris in the oil. The only thing that you can do when you have a situation like this is to clean everything out very carefully, replace the bearing, and button the engine back up. At the time of this writing, we're using the car as a test bed and haven't put it back together yet, but the plan is to fill it up with oil, run it for five or ten minutes, change the oil, and repeat the process a few times to flush the entire system. Unless some chunks of metal found their way past the oil filter, I suspect the engine will be fine: I think we caught the problem in time. For more photos on the destroyed bearing, see Photos 57 through 64 below.

What can be done to fix or prevent a failure?

So what can be done to prevent an IMS bearing failure? Luckily, there are a few solutions available. Firstly, I recommend that you change your oil every 5,000 miles or sooner and use a higher viscosity motor oil that has additional anti-wear additives. Use Porsche approved 5w40 viscosity motor oils, preferably one that carries an API SJ-SL rating. Use of a 0w40 viscosity should be limited to colder climates in winter months, where cold starts are regularly below freezing, for added start up protection. Also consider using an oil with more anti-wear additives (like Zn, P, or moly extreme). Recent regulatory changes in the United States have caused oil companies to revise their formulations of oil and reduce the amount of anti-wear components in them. The reasoning behind this is the belief that these components contribute to premature deterioration of the catalytic converters. I'm not so sure I agree with that premise however. The solution to this problem is to make sure that you run a motor oil with the proper anti-wear formulations, and change your oil often. For more information than you could ever possibly use, check out Charles Navarro's "thesis" on oil analysis on the LN Engineering website.

Also curious is the fact that cars that are driven tamely seem to have more problems than cars that are driven aggressively. Boxster engines that are used at the track are known to have very few problems relating to the bearing, whereas Boxsters driven by "little old ladies" tend to show the most damage. The track-day Boxster bearing longevity may be explained by the fact that these cars often have their oil changed after ever trip to the track.

The best solution to the problem is to replace the bearing prior to its failure. Porsche Club of America tech advisor, Scott Slauson from Softronic (see Pelican Technical Article: Installing Performance DME Map Software) pioneered a procedure that allows you to replace the bearing with the engine still in the car. Building upon that procedure, LN Engineering and Pelican Parts have both developed bearing replacement kits to swap out the troublesome original bearing.

Which Bearing is Inside Your Engine?

The first step in replacing the bearing is to figure out which one you have in your engine. There were three variations installed over the years. Early cars typically have a large double row bearing that has a snap clip inside the bearing. Porsche later went to a single-row bearing design when the timing chain design was modified (see Figure 5 for a comparison of the two). Then, around model year 2006, Porsche installed a third version which is not replaceable. The supposed cut-off on engine numbers are listed in the Porsche factory Technical Bulletins, but unfortunately, these numbers are not 100% accurate, so you need to look at the bearing housing that is installed into your engine in order to be 100% sure as to which bearing you have (see Figure 5).

The question of which bearing is inside your engine is probably the number one question asked when people read this article. Porsche's electronic parts catalog lists the following engine numbers as the cutoffs for the various engines:

Engine Number Model Bearing Type
Up to engine # M 651 12851 Boxster 2.7L M96.22 Double Row Bearing
Up to engine # M 671 11237 Boxster S 3.2L M96.21 Double Row Bearing
Up to engine # M 661 14164 Carrera 996 3.4L Double Row Bearing
From engine # M 651 12852 Boxster 2.7L M96.22 Single Row Bearing
From engine # M 651 11238 Boxster S 3.2L M96.21 Single Row Bearing
From engine # M 661 14165 Carrera 996 3.4L Single Row Bearing
All 2005 Boxster 987 (maybe some 2006 models) Single Row Bearing
All 2005 Carrera 997 (maybe some 2006 models) Single Row Bearing
Maybe some 2006 Cayman models Single Row Bearing

However, as mentioned previously, practical experience has determined that these numbers are not 100% correct. Porsche replaced and/or repaired a lot of engines over the years and as a result there are a lot of engines out there where parts are mixed and matched. For example, the 3.4 Porsche factory motor that I installed in my 3.4L conversion has the very-late style intermediate shaft bearing with the 22mm center nut (see Figure 17), but is missing some other upgrades that had been implemented over the years.

The only way to surely know is to remove your transmission and look. The double-row version of the intermediate shaft was the first version used on these engines, and will almost always be found on the early cars. The intermediate shaft cover for the double-row bearing is characterized by a shallow dish, as shown in Figure 14. The single-row bearings have a much deeper dish, as shown in Figure 15. The backside differences (not visible until you remove them) are shown in Figure 16. The two side-by-side for a comparison are shown in Figure 13. The bottom line is that you cannot typically tell what you have for sure in your engine until you remove the transmission and check.

Pelican Parts Replacement Kit

The Pelican kit is shown in Figure 19, and contains everything that you need to perform the replacement in either a single or dual row bearing engine. The Pelican kit uses the same bearing that Porsche used when originally building the engines, but the Pelican kit incorporates a stronger seal on the outside of the bearing (see Figure 20 and Figure 21). The kit is designed so that the bearing replacement can be performed during a routine clutch replacement (see Pelican Technical Article: Clutch Replacement). Changing out the bearing during each clutch job will ensure that the bearing is fresh and not wearing prematurely. As stated in the previous section, the failure mode of this bearing is not well known: if it's swapped out and replaced every 30,000-45,000 miles when the clutch is renewed, it should protect your engine from problems.

The kit uses a single-row bearing, just like the later-style Porsche design. For engines that originally had a double-row bearing installed, there are two spacers included with the kit (Figure 22). These spacers fill the space that was normally occupied by the double-row bearing. In addition to the bearing replacement, the kit also includes a stronger center stud. Instead of having the o-ring integrated into the stud, the o-ring is placed in a v-shaped sandwich on the outside surface of the bearing housing cover. For a complete visual guide of how the Pelican kit fits together and seals the center stud, see Photos 22 through 37. The Pelican kit has successfully completed prototype testing and is now available at Pelican Parts

LN Engineering Retrofit Kit

This easy-to-install retrofit upgrade kit that can be installed with the engine still in the car, and provides almost bullet-proof reliability to this critical component. This kit costs about $600 and is available online from PelicanParts.com. The upgrade kit incorporates a custom ceramic hybrid bearing (see Figure 41 and Figure 42), featuring precision Japanese-made tool steel races and genuine USA-made Timken sintered silicon nitride ultra-low friction roller balls. This bearing, combined with a beefier center stud, and a custom-machined housing ensures that the IMS problems inherent in the stock design are reduced and mitigated (see Figure 44). The engine can be upgraded during a routine clutch job, and is fairly easy to install thanks to the installation tools designed by LN Engineering specifically for this task.

The engineers at LN Engineering have the following additional comments to say regarding the benefits of the ceramic bearing:

Based off of the knowledge gained from our bearing analysis of both factory single and double-row IMS bearings and significant research, we've employed a custom ceramic hybrid bearing, featuring precision Japanese-made tool steel races and genuine USA-made Timken sintered silicon nitride ultra-low friction roller balls. We use exclusively ceramic hybrid bearings on both our IMS upgrade and retrofit kits. On average up to thirty times more expensive than conventional steel ball bearings, the benefits far outweigh the cost.

Recent improvements in purity and grain structure have given silicon nitride a high stress fatigue life equal to, or better than, that of bearing steels. Some tests have shown life 3 to 5 times that of M-50 steel. Performs up to 15 times longer in poor lubrication environments (like suggested by the bearing analysis above) as compared to steel.

Other benefits include...

Less maintenance - Due to a minimum level of Adhesive Wear, bearing components and lubricants last much longer, saving you expensive service and repair time.

High Hot Strength - High compressive and flexural strength over a wide temperature range. Lends itself for use to 2200 degrees F.

Low Density - Specific density of 3.2 compared to 7.8 for steel. At high bearing operating speeds, the bearing balls have a centrifugal force which may exceed the external loads on the bearing. The low density of ceramics can reduce this load considerably.

High Hardness - While bearing steel is in the RC 58-64 hardness range, silicon nitride has a hardness of RC 75-80 and offers excellent wear resistance and resistance to denting or flat-spotting.

Coefficient of Friction - Silicon nitride has a coefficient of friction which is significantly lower, especially under marginal lubrication conditions. It also exhibits better resistance to scuffing and seizing than bearing steel.

Corrosion Resistance - Silicon nitride is unaffected by most common corrosive agents, and is well-suited for use in hot corrosive atmospheres, or where lubricants have been known to attack conventional bearing steels.

Which kit to use?

I designed the Pelican Parts replacement bearing kit in order to fill a gap within the Do-It-Yourself (DIY) market. This kit is designed to replace the factory bearing with a very similarly manufactured bearing (with an improved seal and updated center bolt). I recommend that the bearing be swapped out each time a clutch replacement is performed (30,000: 45,000 miles). The outer seal is not removed on the kit, instead an improved seal is installed which should offer longer life than the factory original. Replacement bearings, o-rings and parts will be available for customers who have already performed the swap at least once, and already have the tools, spacers, and the improved center bolt. The Pelican Parts kit uses the stock intermediate shaft bearing cover as a way to reduce the total cost of the kit.

The LN Engineering retrofit kit contains a stronger-than-stock center stud, a custom machined intermediate shaft end cover, and a special, custom-manufactured ceramic bearing which is very expensive, but has much longer life under harsh conditions. The LN Engineering kit is considered to be the more robust kit, and is designed primarily for shops that are installing the retrofit and need that extra guarantee for their customers. The extended-life ceramic bearing (see Figure 42) is only available at this time with the LN Engineering kit, and its inclusion is responsible for a large portion of the cost differences between the two kits.

Bearing Removal

Okay, it's time to talk about the procedure involved with replacing the intermediate shaft bearing. The bearing is located behind the flywheel of the engine, so the first step that you need to do is jack up the car (see Pelican Technical Article: Jacking Up and Lifting the Boxster on Jack Stands), and remove the transmission (see Pelican Technical Article: Transmission Removal). Then, remove the clutch and flywheel from the engine (see Pelican Technical Article: Clutch Replacement). With the car elevated in the air, drain the oil out and remove and inspect the oil filter (see Pelican Technical Article: Oil Change).

Before doing anything else, you want to remove the camshaft end plugs from your engine. These plugs cover the camshaft timing marks: you will need to check the timing on the camshafts when you are done with your bearing replacement. If you have a pre-2003 Boxster engine (or pre-2002 for the Carrera 996), then you only need to remove the plugs on the exhaust camshafts (two plugs total). The exhaust camshafts are located on the bottom of the engine. If you have a 2003 or later Boxster engine (2002 or later for the 996 Carrera), then you need to remove all four plugs (intake and exhaust), because you will need to check all four camshafts when you are done. For the Boxster, the plugs for the camshafts that drive cylinders 4-6 should be easily accessible to the left of the flywheel area. The plugs for cylinders 1-3 need to be accessed through the panel in the passenger compartment that gives you access to the drive belts on the engine (see Project 5 for more information). Follow the instructions in Figure 65 and Figure 66 below for details on removing the plugs. The removed plug and camshaft end is shown in Figure 67.

With the plugs removed, now remove the three bolts that hold on the intermediate shaft bearing cover (Figure 68). With the bolts removed, you should be able to shine a flashlight down the holes and see the intermediate shaft sprocket inside the engine (Figure 69). What you are looking at is the big sprocket for the intermediate shaft, as shown in Figure 4. What you want to do is rotate the engine clockwise (Figure 70), until you can find three spots behind these through holes where the metal surface of sprocket is blocking the holes. You may find it easier to rotate the engine if you remove the spark plugs (Pelican Technical Article: Replacing Spark Plugs and Coils). You will then insert set screws into these holes and push the screw into the sprocket, in order to hold it in place while you're performing the bearing replacement. Figure 71 and Figure 72 show two different angles of set screws illustrating this point (it's difficult to explain it by just using text). Rotate the engine until you have found a spot where all three holes are blocked, then install the set screws as shown in Figure 75. Tighten the screws down only hand-tight, but very snug, using a small tool or ratchet. Don't use the iron grip of death here, as you don't want to strip out the small M6 bolts. Just make them very snug and tight with your hand.

With the intermediate shaft sprocket locked in place by the set screws, now is the time that you want to mark the locations of your camshafts. Again, you only need to mark the two exhaust camshafts on the pre-2003 Boxster engines (pre-2002 on the Carrera 996). This is because the intake and exhaust camshafts are tied together with a chain of their own, and if one is properly set, then the other is properly set as well (see Figure 128 for more clarification). If you have a 2003 and later Boxster engine (or 2002 and later 996 Carrera engine), this particular design uses what are known as vane-cell adjusters and a single chain to link both the exhaust and intake camshafts together (see Figure 129). This design has a tendency to have the camshafts slip when performing the replacement, so you need to be vigilant in checking all four camshafts (see the section on checking camshafts at the end of this article).

Use some marking paint, or a scribe to mark the locations of the camshaft with respect to the cylinder head (see Figure 76). Make sure that the marks are clear and visible: you will be rotating the engine 360 degrees when you are done to verify that all of the camshafts line up again with the marks that you created.

With the camshaft timing properly marked and the intermediate shaft secured, it's time to remove the two tensioners that pull on the flywheel-end sprockets of the intermediate shaft. The first one to remove is the tensioner for cylinders 1-3, which is located to the right of the flywheel area and is shown in Figure 77. Next, remove the tensioner that tightens the chain that connects the intermediate shaft to the crankshaft, located to the left of the flywheel area (see Figure 78). Be sure to have an oil catch pan ready when you remove these two tensioners, as oil will spill out.

Next, remove the center nut from the bearing. I have found that these typically just come off with a 13mm socket, but you may have to use an open 13mm wrench and a screwdriver to hold the center of the bolt as you remove the nut (see Figure 79). With the center nut removed, you should be able to slightly tap the cover counter-clockwise so that you can get some pry bars underneath (Figure 80). You will need at least two of them to get the cover off (one just won't work), applying pressure in two places at the same time (Figure 81). There is a special tool available from Porsche to assist in removing the cover, but it's really expensive and not really necessary (Figure 82).

With the cover removed, you should be able to see the bearing underneath. Figure 83 shows an example of a completely destroyed IMS bearing. Picture 85 shows more of what a normal bearing should look like. If you accidentally drop the center bolt into the recesses of the intermediate shaft, then simply pluck it out with a magnetic tool (see Figure 84). If you have a single-row bearing engine, at this point you will want to remove the large circlip that holds the bearing in place (see Figure 86, Figure 87 and Figure 88). If you have a double-row bearing engine, then the internal snap ring will simply snap out automatically when you go to pull the bearing.

There is a specialized bearing removal tool that was developed by the folks at LN Engineering for this task (Figure 91 and Figure 92). Thread the center bar of the tool onto the bearing stud (Figure 89). Thread it all the way down to the base of the bearing (Figure 90). Slide the removal tool canister over the threaded rod and then screw on the large nut that fits on the threaded rod. Apply some motor oil to the nut and the back surface of the tool to ease the removal process, as shown in Figure 93. With the tool in place, hold the threaded rod and turn the nut clockwise to remove the bearing (see Figure 94). Be sure to wear safety glasses, as the tool applies a lot of force to pull the bearing out of the engine. Turn the wrench on the nut until the bearing slides out of the engine. For engines with a dual-row bearing, you will hear a loud pop when the internal snap ring pops out of its groove. Be sure to have a oil catch pan or bucket handy, as a significant amount of oil will most likely exit out of the intermediate shaft bore when you remove the bearing (see Figure 95). Figure 96 shows the bearing removed from the engine.

Inside the intermediate shaft you will most likely find some oil and debris (see Figure 97). Get some paper towels and tape them to the end of a stick and clean out the inside of the intermediate shaft. You can also attach a small rubber hose to the end of your shop vacuum and suck out any debris that might remain in there (see Figure 98 and Figure 99).

There's a small possibility that your bearing center stud may break when attempting to pull the bearing out of the engine. If this happens, then you need to remove the bearing using an internal bearing puller tool, like the Stahlwille one shown in Figure 100.

Bearing Installation

Begin by taking the bearing over to your table vice to press in the center stud. Press in the center stud, taking care only to apply pressing force to the inside bearing race. You can use a regular socket from your toolbox to accomplish this. It does not matter which side of the bearing faces the center stud. See Figure 101 for more details.

Prior to installing the new bearing, verify that your intermediate shaft bore is completely clean and free of debris (Figure 102). Using the bearing installation tool, place the new bearing / stud assembly into the end of the tool, as shown in Figure 103. The tool is designed to hold and constrain the bearing while you install it: you need to push the 12mm nut down the shaft of the tool and spin it onto the center stud's threads, as is shown in Figure 104 and Figure 105.

Prepare for the installation of the new bearing by placing it along with the installation tool in your freezer overnight. The cold temperatures will help to shrink the bearing races and make it easier to install (Figure 106). This is an old trick that is commonly used when installing wheel bearings.

With the bearing and tool assembly combined tightly together, place the bearing into the bore on the intermediate shaft (Figure 107). Verify that the placement of the bearing is completely centered and square to the plane of the engine case (make sure it's not cocked off in any direction, even slightly: Figure 108). With a plastic hammer, carefully tap the bearing into place (Figure 109). It should go in relatively smoothly and without too much effort. Figure 110 shows the new bearing properly installed in the bore of the intermediate shaft.

If you are performing the installation on an engine that uses a double-row bearing, install the outer spacer into the bore as is shown in Figure 111. Then, proceed to install the Spiroloc clip into the groove in the intermediate shaft. The installation of the Spiroloc clip is shown in Figure 112 and Figure 113. When the clip is completely installed into the engine, you can then install the intermediate shaft bearing cover in place. Take the smaller spacer and place it on the cover as shown in Figure 115. Then place the cover on the engine and tap it into place using a small rubber hammer (Figure 116).

If you are performing the installation on an engine that uses a single-row bearing, then you don't need to install any spacers: just simply install the big circlip as shown in Figure 114, and then install the intermediate shaft cover as is shown in Figure 116. With both single and double-row installations, you will want to use a new seal on the cover. If your cover is the older style one with the small black o-ring, you will want to upgrade to the newer style cover and improved seal to guard against leaks (see part number list below). I also like to place a small bit of Curil-T sealant on this seal when I'm installing, just as an added measure of oil-leak protection. The cover can only go on in one orientation: typically the numbers / writing on the later-style covers goes at the bottom. When installing the cover, be careful not to pinch or damage the seal, as it has a tendency to get caught sometimes during the installation process.

If for some reason you are having difficulty driving the intermediate shaft cover into place, then you can use the following procedure to assist you. Use three M6x25 bolts to help guide the cover into place (Figure 117). Place the cover into the bore and tap it down as far as it will go. Then, remove the set screws that you placed earlier (Figure 118). Install the bolts, and then crank each one down in an alternating pattern until the cover is flush with the engine case. When the cover is installed in place, then remove the three M6x25 bolts.

With the cover fully in place, you can now remove the set screws (if you haven't already: see Figure 118). Replace them with new micro-encapsulated bolts from Porsche (Figure 119). The phrase "micro-encapsulated" is a fancy word for bolts that have some sealant on them. It's okay to reuse your old bolts, but be sure that you coat the threads in a sealant like Curil-T or Loctite prior to installation or they will leak. Tighten the bolts down to 8 ft-lbs (11 Nm).

With the cover installed and the cover bolts tightened down and sealed, install the o-ring on the center shaft (Figure 123 for the single-row, Figure 120 for the double-row). I recommend putting a thin layer of Curil-T sealant around this o-ring in order to help seal against leaks. With the o-ring in place, now install the spacer (Figure 124 for the single-row, Figure 121 for the double-row). Finally, install the 12-point nut on the top, tightening it to a maximum of 24 ft-lbs. I also recommend placing a bit of Curil-T sealant underneath this nut. See Figure 125 for the single-row installation, and Figure 122 for the double-row installation.

If you are installing the LN Engineering retrofit kit, then the procedure is almost identical, if not simpler. Install the new intermediate shaft bearing cover in the same manner as described above. Prior to installation, verify that the o-ring that fits in the center of the shaft is in place and undamaged. Install the 12-point nut on the end using some green Loctite flange sealant as an added protection against leaks. Figure 126 shows the LN Engineering ceramic bearing installed in the case with the open no-seal side facing outwards, and Figure 127 shows the retrofit kit intermediate shaft end cover installed in place.

At this time I also recommend that you replace your rear main seal (RMS) with the new, updated version. See the Clutch Replacement article for more details.

Checking Camshaft Timing

With the new bearing installed in place, you are basically done with the installation. Be sure to reinstall / re-tighten your chain tensioners if you loosened them up, or removed them during the installation process.  At this point, it's very important that you check your camshaft timing prior to reinstalling the transmission and starting the engine. Figure 128 and Figure 129 show how the timing chains are oriented and setup on the 5-chain (Boxster thru 2002, 996 Carrera thru 2001) and 3-chain motors (Boxster 2003 and later, 996 Carrera 2002 and later). Particularly with the 3-chain motors, you need to make sure that you check the exhaust camshaft for cylinders 1-3 (located to the right of the flywheel). This particular camshaft has the least amount of chain wrap and removing the chain tensioner to perform the replacement has the potential to loosen the chain and allow the timing to skip a tooth on the sprocket.

To check the timing simply take the crankshaft and rotate it 360 degrees from where you originally placed it when you installed the set screws (Figure 60). Then check the marks that you made on the camshafts (four marks on all four camshafts for the 3-chain motors, two marks on the exhaust camshafts for the 5-chain motors). If all of the marks line up perfectly (see Figure 136, Figure 137, and Figure 138), then you're golden, and you can continue with the process. If any of the marks are off, then there is the potential that the timing chain slipped off of the camshaft sprocket during the installation process. See Project 16 for more information on retiming the camshafts if this happens.

If you happen to have the P253 camshaft timing tool, you can use that to check the timing on the 5-chain engines. Simply place the engine at Top Dead Center (Figure 132), remove all four green caps on the camshafts, and install the tool on each side to check each pair of camshafts (Figure 135). If the tool fits, then the timing is perfect. If it doesn't fit, then you will have to retime the cams (see Pelican Technical Article: Camshaft Upgrade / Chain Tensioner Replacement). It's very good practice to check the timing on the 5-chain motors, but in reality, very few of these have problems, unless the instructions were not followed correctly. Still, I recommend checking the timing prior to reinstalling the transmission: it's cheap insurance.

When you're done, carefully rotate the engine a full 360 degrees and check the camshaft timing marks that you made before you started. If they all line up, then you're good to go. If they are off, then your timing chain skipped, and you need to retime your cams. See Project 16 for more details on this procedure.

After you're done checking the camshafts, install new camshaft end caps as shown in Figure 139, Figure 140 and Figure 141. Although I like to use a bit of sealant everywhere, these end caps don't tend to leak.

Also important to note, if you have the camshaft tools handy, you might want to check your camshaft timing *prior* to beginning the installation of the bearing. If the timing is slightly off and the bearing appears fine, then you might have some additional problems in your camshaft timing chain mechanism (slipping sprockets on the intermediate shafts, worn pads on the camshaft solenoid mechanisms, etc.). I would advise investigating these problems prior to pulling out the bearing.

At the time of this writing (June 2010), I'm working on developing some cheaper camshaft locking tools that will allow you to lock all of the camshafts on the engine. The two tools will work either on the 3-chain or 5-chain motors and will only cost about $20 (the factory tools cost about $200 each at this time). Stay tuned, and keep watching the Pelican site and this article for more details.

Don't forget to change the filter and add oil! See Project 2 for more details. If you pulled your bearing and found some major wear or damage, then you probably want to pull the bottom sump off and clean it out (see Pelican Technical Article: Oil Pan Gasket Replacement / Deep Sump Installation). Also think seriously about replacing your sump air-oil separators, as they tend to get contaminated too if you have bearing debris in your sump.

Well, there you go. I think this article is currently the most comprehensive collection of information about the intermediate shaft bearing replacement. If you have any comments or questions, feel free to add them to this thread in our forums. Or, simply write them in the comments section below.

Description Part Number Qty Photo
LN Engineering IMS retrofit kit, single-row bearing engines LN-106-08-2 1 Figure 39
LN Engineering IMS retrofit kit, double-row bearing engines LN-106-08-4 1 Figure 38
Pelican Parts IMS replacement kit PEL-IMS-1 1 Figure 19
LN Engineering IMS bearing removal tool / installation tool set LN-106-08-13 1 Figure 91
Camshaft timing tool for 5-chain engines PEL-TOL-P253 1 Figure 134
Camshaft timing tool for 3-chain engines, P9686 (Figure 137) 000-721-968-60-OEM 1 Figure 137
IMS cover, double-row bearing 996-105-017-02-M100 1 Figure 14
IMS cover, single row bearing 996-105-024-01-M100 1 Figure 15
Improved intermediate shaft cover seal 996-105-112-01-M100 1 Figure 12
Air oil separator 996-107-080-54-OEM 2 Figure 56
Seal for air oil separator 999-701-789-40-OEM 2 Figure 56
IMS micro-encapsulated cover bolts (M6x20) 999-217-150-09-OEM 3 Figure 119
Replacement center nut for stock IMS bearing setup
 (not used unless you're simply replacing your cover seal)
900-380-019-02-OEM 1 Figure 1
Camshaft end plug/seal (green) 996-104-215-54-M100 4 Figure 141
Aluminum crush washers for chain tensioners 900-123-147-30-OEM 2 Figure 77
Curil-T Sealant PEL-246948    

It all starts here with the intermediate shaft cover, located right under the rear main seal (located behind the clutch and flywheel).
Figure 1

It all starts here with the intermediate shaft cover, located right under the rear main seal (located behind the clutch and flywheel). This bearing design has caused a lot of problems with these engines over the past decade. The good news is that the bearings are now fixable using a variety of upgrade / replacement kits designed by engineers working for aftermarket companies like Pelican Parts and LN Engineering.

Here's a photo of an M96 engine intermediate shaft removed from the engine.
Figure 2

Here's a photo of an M96 engine intermediate shaft removed from the engine. This end of the shaft drives the oil pump, and also the camshafts for cylinders 4-6.

Here's a close-up of the intermediate shaft sprocket that drives cylinders 4-6.
Figure 3

Here's a close-up of the intermediate shaft sprocket that drives cylinders 4-6.

Here's a photo of the intermediate shaft showing the center bore where the bearing sits.
Figure 4

Here's a photo of the intermediate shaft showing the center bore where the bearing sits. When you use the set screws to hold the shaft in place (see Figure 70), they push against the surface on the sprocket shown approximately by the green arrow.

This photo shows the single-row bearing next to the double-row bearing (right).
Figure 5

This photo shows the single-row bearing next to the double-row bearing (right). The double-row bearing still has the snap ring attached in the groove of the bearing. The double row bearing was used on all of the early engines until Porsche made a switch to a different chain design. Unfortunately, the cutoff period for this change is not entirely accurate in the Porsche specifications, so it's best to actually take a look at what your intermediate shaft bearing cover looks like to determine which sized bearing you have installed. You'd also think that the double-row bearings would be more durable than the single rows, but that is not the case: they both fail at about the same rate (which indicates that the failure mechanism is not related to the load applied to the bearing).

This is a photo of a replacement bearing.
Figure 6

This is a photo of a replacement bearing. This bearing is manufactured by NSK and is nearly identical to the one used by Porsche for the single-row design. This bearing has the same style outer seal (the black rubber, shown by the green arrow). The Pelican Parts IMS replacement kit has a brown bearing seal that is a double-edged seal that is designed to be an improvement that prevents engine oil from entering the bearing.

Here are the two center bolts shown side-by-side for comparison.
Figure 7

Here are the two center bolts shown side-by-side for comparison. The improved bolt is on the left, and the original Porsche one is on the right. The original one has two grooves cut into it, which create stress risers that may cause the bolt to break. As the bearing weakens, the loads, vibration, and stress placed upon this stock center bolt increases. The result can often be that the bolt sheers, and the engine skips timing, which results in immediate destruction of the entire engine.

Here's a photo showing a stress analysis performed on the stock Porsche intermediate shaft bolt.
Figure 8

Here's a photo showing a stress analysis performed on the stock Porsche intermediate shaft bolt. The analysis shows that the cutout for the o-ring creates a significant stress riser that can fatigue the bolt. Most of the time, the bolt is fine, but if the bearing starts to fail, then the vibration and additional stress on the bolt will often cause it to break. If it does break, you must pull the bearing using a Stahlwille internal bearing puller (see Figure 100).

Shown here are the late and early style intermediate shaft cover plates.
Figure 9

Shown here are the late and early style intermediate shaft cover plates. On the early engines, these covers leaked all of the time (possibly due to excess vibration from the bearing beginning to fail?). In fact, many leaks that were blamed on the rear main seal (RMS) were actually leaks from this intermediate shaft cover. The original cover only had a simple o-ring installed on the outer edge. In later years, Porsche redesigned the cover to incorporate a thicker, three-ridge seal, shown on the left. This improved design can be installed on any early engine, and is recommended if you're replacing the bearing.

This photo shows the troublesome o-ring that was found on the early intermediate shaft bearing covers (double row).
Figure 10

This photo shows the troublesome o-ring that was found on the early intermediate shaft bearing covers (double row).

This photo shows the improved seal design used on the cover for the double-row engines.
Figure 11

This photo shows the improved seal design used on the cover for the double-row engines.

Here's a close-up photograph of the improved three-ridge seal.
Figure 12

Here's a close-up photograph of the improved three-ridge seal. If you pull off your intermediate shaft cover and you find that you have the early style, then I highly recommend that you upgrade to this later-style cover (part numbers listed at the end of this article).

Shown here are two late-style intermediate shaft covers.
Figure 13

Shown here are two late-style intermediate shaft covers. The cover on the left has a deep dish and is used in engines that originally had a single row bearing. The cover on the right is shallower and is used with engines that originally had a double row bearing. Unfortunately, the records on which engine used which style of bearing is very spotty, so the only real way you can tell is by removing the transmission and seeing what you have installed in there.

Here's a close-up view of the intermediate shaft cover for the double-row bearing engines.
Figure 14

Here's a close-up view of the intermediate shaft cover for the double-row bearing engines. The shallower dish is shown by the blue arrow.

Shown here is a brand new intermediate shaft cover plate for the single row bearing engines.
Figure 15

Shown here is a brand new intermediate shaft cover plate for the single row bearing engines. These covers have a very deep dish in the center, shown by the green arrow.

Shown here is the backside of two late-style intermediate shaft covers with the improved seal design.
Figure 16

Shown here is the backside of two late-style intermediate shaft covers with the improved seal design. The cover on the left is for use in engines with the single-row bearing. The one on the right is for use in double-row engines. The main difference between the two of them is the ridge shown by the arrows.

This is a photo of the very late-style intermediate shaft cover.
Figure 17

This is a photo of the very late-style intermediate shaft cover. The most obvious characteristic of this design is the very large nut that fits on the center bolt. The bearing behind the intermediate shaft cover shown here is not removable (it's too big to get out of the bore in the case). These are installed on Porsche rebuilt motors, and later style M96/M97 motors. If you see this large nut, then simply leave it alone: you cannot remove the bearing without splitting the engine case.

Sometimes you can detect a failing intermediate shaft bearing by running a test showing camshaft deviations.
Figure 18

Sometimes you can detect a failing intermediate shaft bearing by running a test showing camshaft deviations. Using the Durametric tool, or a PST-2, you can setup the screen to log camshaft deviation as a function of ignition timing and rpm. Significant variations between the left and right camshaft banks can be a sign of trouble with the bearing. In this graph, the deviation is zero, which is perfect and not indicative of a problem.

Figure 19

This photo shows some of the parts contained in the Pelican Parts Intermediate Shaft Bearing Update Kit: A- Improved center bearing bolt B- Outer race spacer (for engines with double-row bearings) C- Inner race spacer (for engines with double-row bearings) D- Replacement intermediate shaft bearing (NSK) E- Center bolt o-ring F- Center bolt nut G- Long Center bolt spacer (for engines with single-row bearings) H- Short Center bolt spacer (for engines with double-row bearings) I- Snap ring (for engines with single-row bearings) J- Spiroloc snap ring (for engines with double-row bearings) (not shown): three new micro-encapsulated cover bolts, 3 M6x25 installation helper bolts, 3 M6x1x25mm set screws

We're currently looking at replacing the original-style Porsche bearing with one with an upgraded seal (brown) for use in the Pelican Parts replacement kit.
Figure 20

We're currently looking at replacing the original-style Porsche bearing with one with an upgraded seal (brown) for use in the Pelican Parts replacement kit. This seal supposedly is better for protecting the bearing in harsh environments like the inside of an engine.

Here's a shot of the bearing that we're considering for the kit, with the improved seal removed.
Figure 21

Here's a shot of the bearing that we're considering for the kit, with the improved seal removed. This seal is supposed to be tougher and more resilient - we're currently testing it out on our project cars.

Here's a photo showing the two spacers that are used to install the single-row bearing replacement into a car that originally had a double-row bearing installed.
Figure 22

Here's a photo showing the two spacers that are used to install the single-row bearing replacement into a car that originally had a double-row bearing installed. These two precision spacers are manufactured out of steel, and are precision ground to be the exact tolerances that you need to emulate the housing of the double-row bearing.

Here is a photo of the improved center bearing bolt.
Figure 23

Here is a photo of the improved center bearing bolt. This bolt is much stronger than the original and does not suffer from any weak points like the original Porsche design.

Shown here is the long center bolt spacer for engines with single-row bearings.
Figure 24

Shown here is the long center bolt spacer for engines with single-row bearings. The secret to keeping oil from leaking out of the bearing assembly lies with the v-groove precision machined into the spacer. This design squeezes the o-ring tightly against the intermediate shaft cover plate and the bolt, creating a leak-resistance seal. This design element is very similar to the v-groove washers used on the case through-bolts that are installed in the 1965-89 Porsche 911 air cooled engines.

This photo shows the new bearing with the improved center bolt pressed into the inner race.
Figure 25

This photo shows the new bearing with the improved center bolt pressed into the inner race.

Here's a side view of the upgrade kit installed on the intermediate shaft bearing cover used with the double-row bearing engines.
Figure 26

Here's a side view of the upgrade kit installed on the intermediate shaft bearing cover used with the double-row bearing engines. No spacers are installed to illustrate where exactly they are needed. This cover has the updated brown seal.

This photo shows the double-row bearing upgrade kit spacers placed on top of the inner and outer races of the replacement bearing.
Figure 27

This photo shows the double-row bearing upgrade kit spacers placed on top of the inner and outer races of the replacement bearing.

Here's a side view of the upgrade kit installed with spacers on the intermediate shaft bearing cover used with the double-row bearing engines.
Figure 28

Here's a side view of the upgrade kit installed with spacers on the intermediate shaft bearing cover used with the double-row bearing engines. This cover has the updated brown seal.

This photo shows the improved bearing bolt installed along with the new bearing into the double-row intermediate shaft bearing cover.
Figure 29

This photo shows the improved bearing bolt installed along with the new bearing into the double-row intermediate shaft bearing cover.

This photo shows how the o-ring fits on the new bolt (this o-ring is installed after the bearing is installed into the engine).
Figure 30

This photo shows how the o-ring fits on the new bolt (this o-ring is installed after the bearing is installed into the engine). This is for the double-row bearing cover.

This photo shows how the short spacer fits over the o-ring.
Figure 31

This photo shows how the short spacer fits over the o-ring. This is for the double-row bearing cover.

Here's how the finished assembly should look when the nut is tightened down on the improved center bolt (double-row bearing cover shown).
Figure 32

Here's how the finished assembly should look when the nut is tightened down on the improved center bolt (double-row bearing cover shown).

Here's a side view of the upgrade kit installed on the intermediate shaft bearing cover used with the single-row bearing engines.
Figure 33

Here's a side view of the upgrade kit installed on the intermediate shaft bearing cover used with the single-row bearing engines. This cover has the updated seal.

This photo shows the improved bearing bolt installed along with the new bearing into the single-row intermediate shaft bearing cover.
Figure 34

This photo shows the improved bearing bolt installed along with the new bearing into the single-row intermediate shaft bearing cover.

This photo shows how the o-ring fits on the new bolt (this o-ring is installed after the bearing is installed into the engine).
Figure 35

This photo shows how the o-ring fits on the new bolt (this o-ring is installed after the bearing is installed into the engine). This is for the single-row bearing cover.

This photo shows how the longer spacer fits over the o-ring.
Figure 36

This photo shows how the longer spacer fits over the o-ring. This is for the single-row bearing cover.

Here's how the finished assembly should look when the nut is tightened down on the improved center bolt (single-row bearing cover shown).
Figure 37

Here's how the finished assembly should look when the nut is tightened down on the improved center bolt (single-row bearing cover shown).

This photo shows the LN Engeering IMS retrofit kit with a dual row bearing.
Figure 38

This photo shows the LN Engeering IMS retrofit kit with a dual row bearing. Although this bearing is not exactly the same size as the one originally used in the engine, the specially machined bearing cover supports the bearing in a similar manner. The bearing is locked in place using a Spiroloc snap ring.

Here is a photo showing the complete LN Engineering IMS retrofit kit for engines with single row bearings.
Figure 39

Here is a photo showing the complete LN Engineering IMS retrofit kit for engines with single row bearings.

Shown here is the extremely durable ceramic bearing used by LN Engineering in their IMS replacement kit.
Figure 40

Shown here is the extremely durable ceramic bearing used by LN Engineering in their IMS replacement kit. The bearing contains ceramic balls that feature precision Japanese-made tool steel races and genuine USA-made Timken sintered silicon nitride ultra-low friction roller balls. These bearings cost up to thirty times more than conventional steel ball bearings, however the benefits far outweigh the cost.

This photo shows the LN Engineering ceramic bearing with the outer seal removed.
Figure 41

This photo shows the LN Engineering ceramic bearing with the outer seal removed. The engineers at LN Engineering have theorized that the removal of the seal will allow fresh motor oil to lubricate the ceramic bearing, thus they have removed the seal from the rear-facing side of the bearing.

LN Engineering's kit uses a custom ceramic bearing.
Figure 42

LN Engineering's kit uses a custom ceramic bearing. Here's what they have to say about the benefits: Recent improvements in purity and grain structure have given silicon nitride a high stress fatigue life equal to, or better than, that of bearing steels. Some tests have shown life 3 to 5 times that of M-50 steel. Performs up to 15 times longer in poor lubrication environments (like suggested by the bearing analysis above) as compared to steel. Other benefits include... Less maintenance - Due to a minimum level of Adhesive Wear, bearing components and lubricants last much longer, saving you expensive service and repair time. High Hot Strength - High compressive and flexural strength over a wide temperature range. Lends itself for use to 2200 degrees F. Low Density - Specific density of 3.2 compared to 7.8 for steel. At high bearing operating speeds, the bearing balls have a centrifugal force which may exceed the external loads on the bearing. The low density of ceramics can reduce this load considerably. High Hardness - While bearing steel is in the RC 58-64 hardness range, silicon nitride has a hardness of RC 75-80 and offers excellent wear resistance and resistance to denting or flat-spotting. Coefficient of Friction - Silicon nitride has a coefficient of friction which is significantly lower, especially under marginal lubrication conditions. It also exhibits better resistance to scuffing and seizing than bearing steel. Corrosion Resistance - Silicon nitride is unaffected by most common corrosive agents, and is well-suited for use in hot corrosive atmospheres, or where lubricants have been known to attack conventional bearing steels.

Here's a photo of the LN Engineering intermediate shaft retrofit kit installed onto the end of a spare intermediate shaft (seal missing from the cover).
Figure 43

Here's a photo of the LN Engineering intermediate shaft retrofit kit installed onto the end of a spare intermediate shaft (seal missing from the cover).

Here's a neat side / cutaway view of the intermediate shaft and the LN Engineering IMS retrofit kit installed.
Figure 44

Here's a neat side / cutaway view of the intermediate shaft and the LN Engineering IMS retrofit kit installed. This photo shows the intermediate shaft upgrade kit installed into a display Boxster engine with one half of the engine case missing. Shown here are the intermediate shaft timing chain (blue arrow), the intermediate shaft gear (yellow arrow), the intermediate shaft bearing cover/housing (red arrow), the housing-to-crankcase seal (orange arrow), one of the three bolts that attach the housing to the case (purple arrow), and the engine case (white arrow). The bearing stud and nut are also shown installed in the center of the housing.

If you're having your engine rebuilt, you can send out your intermediate shaft to LN Engineering and they will custom machine your shaft for the installation of multiple bearings.
Figure 45

If you're having your engine rebuilt, you can send out your intermediate shaft to LN Engineering and they will custom machine your shaft for the installation of multiple bearings.

This photo shows a completely destroyed intermediate shaft bearing (IMS).
Figure 47

This photo shows a completely destroyed intermediate shaft bearing (IMS). The outer seal and race are missing. The balls have fallen down in the bearing and are basically just sitting there. This engine was very close to self-destructing: it was wise for the owner to turn it off and not drive it any more. As a result, he may have saved the engine from complete destruction. However, the remains of the bearing have circulated out of this area and down to the engine sump: if any metallic particles got past the filter, then they would have caused damage to the rest of the engine (bearings, etc.).

Here's a closer shot of the damaged bearing.
Figure 48

Here's a closer shot of the damaged bearing. As you can see from this photo, the balls themselves are pitted and no longer round. I was able to successfully pull this bearing out of the bore, but there was a chance that I might have been able to pull only the inner race out and could have been left with the outer race still stuck in the intermediate shaft. If that were the case, then I would have needed a special bearing puller to remove the outer race.

Here's a closer shot of the inside of the intermediate shaft with the bearing removed.
Figure 49

Here's a closer shot of the inside of the intermediate shaft with the bearing removed. As you can see, there are some remains of the bearing still inside the tube. Be sure to clean out the tube carefully and thoroughly prior to installing the new bearing.

Sometimes you can see the signs of an intermediate shaft bearing failure.
Figure 50

Sometimes you can see the signs of an intermediate shaft bearing failure. Here's what the oil filter looked like when we removed it from our Carrera 996 engine. You can clearly see small flakes of metal in the filter. It looks like the filter did a pretty good job of blocking the particles. Our plan is to clean the sump, replace the bearing and the lower sump air-oil separators, flush the motor with oil a few times and then put some miles on the engine. Since this was caught in time, we anticipate that the engine should be fine.

Here's a close-up shot of the oil filter with all of the particles from the bearing contained inside.
Figure 51

Here's a close-up shot of the oil filter with all of the particles from the bearing contained inside.

With so much damage to the intermediate shaft bearing, we decided to pull the bottom engine sump off of the car.
Figure 52

With so much damage to the intermediate shaft bearing, we decided to pull the bottom engine sump off of the car. This car only had 31,000 miles on it, so I found it a bit suspicious that the oil pan had been removed and then resealed with the wrong type of sealant (see the grey bead around the pan). For the proper method of resealing the pan, see Pelican Technical Article: Oil Pan Gasket Replacement / Deep Sump Installation.

Here's what the bottom of the sump looked like when we pulled it off to check for debris (see <a style=color:000080 href=http://www.
Figure 53

Here's what the bottom of the sump looked like when we pulled it off to check for debris (see Pelican Technical Article: Oil Pan Gasket Replacement / Deep Sump Installation). As you can see, there are a lot of metal bits and pieces here. We will be cleaning this up carefully and then flushing the engine with fresh oil several times: hopefully none of these metal flakes made it up through the engine and past the oil filter.

Here's a close-up shot of all of the bearing debris that was found in the sump.
Figure 54

Here's a close-up shot of all of the bearing debris that was found in the sump.

Lots of debris ended up getting caught in the oil pickup screen, which is a good thing.
Figure 55

Lots of debris ended up getting caught in the oil pickup screen, which is a good thing. For the smaller bits and pieces, an inspection of the oil filter (Figure 51) revealed smaller flakes of material.

The bottom of the sump contains two air-oil separators that suck up oil and prevent the oil from foaming.
Figure 56

The bottom of the sump contains two air-oil separators that suck up oil and prevent the oil from foaming. Since this area was contaminated with oil, we decided it would be wise to replace these two units. Both the left and right ones are identical and cost about $35 each (shown with purple arrows).

Here are the remains of the bearing after we removed it.
Figure 57

Here are the remains of the bearing after we removed it. It fell apart in my hand taking it out of the removal tool. We still didn't find the remains of the other rubber seal anywhere.

This photo shows the inner race of the bearing and some of the balls.
Figure 58

This photo shows the inner race of the bearing and some of the balls. You can see the balls are pitted and damaged.

The outer race retainer wrapped itself around the intermediate shaft bearing cover and scratched it quite a bit.
Figure 59

The outer race retainer wrapped itself around the intermediate shaft bearing cover and scratched it quite a bit. Although this is the updated cover (it had obviously been previously replaced on this car), we're not going to reuse it since it's damaged.

The red arrow shows some extreme pitting on the outer race of the double-row bearing.
Figure 60

The red arrow shows some extreme pitting on the outer race of the double-row bearing.

Here's the ball retainer, looking pretty chewed up.
Figure 61

Here's the ball retainer, looking pretty chewed up.

Here's another shot of the intermediate shaft bearing cover where it's been damaged by the remains of the bearing.
Figure 62

Here's another shot of the intermediate shaft bearing cover where it's been damaged by the remains of the bearing. In reality, this cover could probably be cleaned up and reused if absolutely necessary. I would use a new seal of course in the installation process.

Here's the inner race of the damaged bearing showing pitting and wear (green arrow).
Figure 63

Here's the inner race of the damaged bearing showing pitting and wear (green arrow).

Here's another photo of a dual row bearing that experienced complete destruction.
Figure 64

Here's another photo of a dual row bearing that experienced complete destruction. Note the pitting and scarring on the balls.

Use a pick tool to poke a hole in the center of the camshaft end cover and then pull it out.
Figure 65

Use a pick tool to poke a hole in the center of the camshaft end cover and then pull it out.

There is metal washer-style ring that is located in the camshaft end plug: use a screwdriver to enlarge the hole in the center and pull it out.
Figure 66

There is metal washer-style ring that is located in the camshaft end plug: use a screwdriver to enlarge the hole in the center and pull it out.

With the end cover removed, you can see the end of the camshaft, along with the timing slot.
Figure 67

With the end cover removed, you can see the end of the camshaft, along with the timing slot. Prior to removing the intermediate shaft bearing cover, mark each of the four camshafts with respect to the case. This way, you can visibly see if the camshafts have moved or "jumped time" when you were installing the bearing.

Using a 10mm socket, remove the three bolts that hold on the intermediate shaft cover.
Figure 68

Using a 10mm socket, remove the three bolts that hold on the intermediate shaft cover. There's quite a bit of oil residue on the lower half of the cover, which seems to indicate that there is some leakage from the seal. While not a sign that the bearing is bad, it's also not a terribly good sign either.

The holes that hold on the intermediate shaft cover are through-holes, which means they exit out into the engine case.
Figure 69

The holes that hold on the intermediate shaft cover are through-holes, which means they exit out into the engine case. You want to rotate the crankshaft until you see metal appear behind each of these holes. The intermediate shaft has some large relief holes cut in the big sprocket (see Figure 4). You want to rotate the engine until all of the small little holes here are blocked by metal on the sprocket. This way, none of the set screws will go into one of the larger holes on the sprocket. When you install the set screws, they should firm up just below the surface of the case. If they don't then make sure you don't keep turning them: you may end up dropping them into your engine case, which will make them *very* difficult to retrieve later on.

Use a 24mm socket on a large driver to turn the crankshaft over.
Figure 70

Use a 24mm socket on a large driver to turn the crankshaft over. You might find it easier to turn the car over if you remove the spark plugs (see Pelican Technical Article: Replacing Spark Plugs and Coils).

The yellow arrow shows how the set screw pushes against the sprocket surface and holds it in place.
Figure 71

The yellow arrow shows how the set screw pushes against the sprocket surface and holds it in place. When you're rotating the engine, you want all three set screws to be pushing on the surface of the sprocket, not pushing through one of the open holes (green arrow).

Here's another photo of the right side showing how the set screws secure the shaft in place.
Figure 72

Here's another photo of the right side showing how the set screws secure the shaft in place. The screws act just as a friction fit to keep the shaft from moving or rotating while you're working on it.

These are the set screws that I used to keep the intermediate shaft in place while removing the end cover.
Figure 73

These are the set screws that I used to keep the intermediate shaft in place while removing the end cover. They are DIN916 M6 1.00 x 25 length.

Close-up of the M6x1x25mm set screws that fit perfectly for this task.
Figure 74

Close-up of the M6x1x25mm set screws that fit perfectly for this task.

After the three bolts that hold on the cover are removed and you've lined up the gear behind the cover, insert the set screws into the holes and tighten them down.
Figure 75

After the three bolts that hold on the cover are removed and you've lined up the gear behind the cover, insert the set screws into the holes and tighten them down. Don't use the iron-grip-of-death to tighten them down, they only need to be hand tight. With the set screws in place, you should be able to tap the cover and rotate it back and forth in its bore a bit.

With the set screws in place, mark the camshafts with some marking ink or paint.
Figure 76

With the set screws in place, mark the camshafts with some marking ink or paint. Mark the two intake camshafts for pre-2003 engines, and mark all four for 2003 and later engines. The pre-2003 engines had the intake and exhaust camshafts tied together with a separate chain, so if one camshaft is properly timed, then the other one should be as well. You want to mark the camshafts to make sure that they do not move or rotate while you're doing the installation and alter the timing of the engine. When you're done with the installation, you will rotate the engine 360 degrees and double-check to make sure these marks all line up again perfectly.

You need to release a bit of the tension on the camshaft chains by unscrewing the tensioners out of their bore just a bit.
Figure 77

You need to release a bit of the tension on the camshaft chains by unscrewing the tensioners out of their bore just a bit. Use a 32mm wrench or socket to release the right side chain tensioner, and remove it from its bore. The right side tensioner is located in

In a similar manner, loosen up the right side chain tensioner, which is located on the right side cylinder head (near the 4-6 cylinder head).
Figure 78

In a similar manner, loosen up the left side chain tensioner, which is located in the side of the engine block (near the 4-6 cylinder head). This chain tensioner tightens the chain that connects the intermediate shaft to the crankshaft.

You can sometimes simply use a 13mm socket to remove the nut that fixes the cover and bearing in place.
Figure 79

You can sometimes simply use a 13mm socket to remove the nut that fixes the cover and bearing in place. If the shaft spins, then you need to secure it with a screwdriver and use a wrench.

With the center nut off, tap the cover a bit counter-clockwise (in the direction of the yellow arrow) so that you can get your prybar in there.
Figure 80

With the center nut off, tap the cover a bit counter-clockwise (in the direction of the yellow arrow) so that you can get your prybar in there. Work each ear a little bit at a time until the cover is ready to pop off.

This photo shows the intermediate shaft cover / housing with the three bolts removed, and the center nut disconnected.
Figure 81

This photo shows the intermediate shaft cover / housing with the three bolts removed, and the center nut disconnected. Use two small prybars to remove the cover from the engine. The cover shown installed in this engine is a shallow one, meaning that this engine has a double-row bearing inside.

Here's a photo of the crazy expensive and complicated factory removal tool for the bearing cover.
Figure 82

Here's a photo of the crazy expensive and complicated factory removal tool for the bearing cover. The tool clamps onto the edges that are machined in the cover and then carefully pulls the cover off of the case. The tool is nice, but the removal of the cover can be accomplished with a set of pry bars and some careful pulling.

Here's what I found when I removed the cover.
Figure 83

Here's what I found when I removed the cover. This intermediate shaft bearing is completely trashed. The seal and race are no longer attached to the bearing (the race was stuck on the shaft of the cover), and the ball bearings are just hanging out at the bottom of the bearing. This is a double-row bearing, so it looks like the 2nd race of the bearing (located in the back) was all that was keeping this together as we ran the car. Full, complete destruction of the engine was going to happen very soon if the engine was run for any length of time.

If the main bearing bolt falls in the recesses of the intermediate shaft, simply use a magnetic pickup tool to retrieve it and pull it out.
Figure 84

If the main bearing bolt falls in the recesses of the intermediate shaft, simply use a magnetic pickup tool to retrieve it and pull it out.

Here's a shot of the double-row intermediate shaft bearing cover removed and the shaft constrained by the three set screws (see arrows).
Figure 85

Here's a shot of the double-row intermediate shaft bearing cover removed and the shaft constrained by the three set screws (see arrows).

Here's a shot of the single-row intermediate shaft bearing cover removed and the shaft constrained by the three set screws.
Figure 86

Here's a shot of the single-row intermediate shaft bearing cover removed and the shaft constrained by the three set screws.

For engines with the single row bearing, the bearing is held in place against the intermediate shaft by a big circlip.
Figure 87

For engines with the single row bearing, the bearing is held in place against the intermediate shaft by a big circlip. Using a set of circlip pliers, remove this clip (use safety glasses when performing this step).

Here is the big circlip removed from the single-row bearing.
Figure 88

Here is the big circlip removed from the single-row bearing.

This photo shows the threaded rod and adapter piece attached to the center bolt of the intermediate shaft bearing.
Figure 89

This photo shows the threaded rod and adapter piece attached to the center bolt of the intermediate shaft bearing. Since this particular bearing is trashed, the hope was that the balls would stay in place long enough for the bearing to be pulled out in one piece (it did work successfully).

Install the bearing removal tool onto the center stud by threading the center rod piece onto the center bolt that holds the bearing and the cover plate together.
Figure 90

Install the bearing removal tool onto the center stud by threading the center rod piece onto the center bolt that holds the bearing and the cover plate together. Make sure that you thread the hexagon shaped piece down as far as it can go onto the bolt.

Shown here is the bearing removal tool (left) and the installation tool (right), as designed and manufactured by LN Engineering.
Figure 91

Shown here is the bearing removal tool (left) and the installation tool (right), as designed and manufactured by LN Engineering. The two tools are typically sold as a kit and are very effective at removing and installing the bearing properly.

Here's a photo of the front of the bearing removal tool that shows where the center bolt connects to the threaded rod (arrow).
Figure 92

Here's a photo of the front of the bearing removal tool that shows where the center bolt connects to the threaded rod (arrow).

With the center rod attached to the intermediate shaft bolt, slide on the outer cylinder and spin on the nut to the threaded rod.
Figure 93

With the center rod attached to the intermediate shaft bolt, slide on the outer cylinder and spin on the nut to the threaded rod. I found it most useful to lubricate the back surface of the cylinder and the nut too in order to facilitate easier turning of the nut (lubricate at the area shown by the arrow).

With a 24mm wrench and a breaker bar + 13mm socket combo, hold the center shaft in place (green arrow) while turning the wrench clockwise (yellow arrow).
Figure 94

With a 24mm wrench and a breaker bar + 13mm socket combo, hold the center shaft in place (green arrow) while turning the wrench clockwise (yellow arrow). This will slowly pull the IMS bearing out of the bore of the intermediate shaft. For the double-row bearings, you will need to apply quite a lot of force. You will also hear a loud "POP" sound as the retaining ring snaps out of place. After this pop, the amount of force to remove and pull out the bearing should be moderate.

Be sure to have an oil catch bucket or pan handy, as the intermediate shaft is often full of oil.
Figure 95

Be sure to have an oil catch bucket or pan handy, as the intermediate shaft is often full of oil. When you remove the bearing, all of this oil will come pouring out of the engine.

Success! The bearing came out with out any trouble using the LN Engineering bearing puller tool.
Figure 96

Success! The bearing came out with out any trouble using the LN Engineering bearing puller tool. When the bearing finally pops out of the intermediate shaft, the tool will come loose so be ready to grab it.

Here's a closer shot of the inside of the intermediate shaft with the bearing removed.
Figure 97

Here's a closer shot of the inside of the intermediate shaft with the bearing removed. As you can see, there are some remains of the bearing still inside the tube. Using some paper towels taped to the end of a stick, carefully clean out the inside of the shaft (don't leave any paper towels inside).

When done cleaning with the towels, attach a small hose to the end of your shop vacuum and also vacuum out any leftover debris that may remain inside the tube.
Figure 98

When done cleaning with the towels, attach a small hose to the end of your shop vacuum and also vacuum out any leftover debris that may remain inside the tube.

It's very important to get all of the metallic debris and residue out of the center of the shaft so that it doesn't find its way to the rest of your engine.
Figure 99

It's very important to get all of the metallic debris and residue out of the center of the shaft so that it doesn't find its way to the rest of your engine.

If your center stud breaks, then you will need to use an internal bearing puller like the one shown here.
Figure 100

If your center stud breaks, then you will need to use an internal bearing puller like the one shown here. This puller, manufactured by Stahlwille expands on the inside race of the bearing and then allows the puller to extract it from the case.

If the center bolt is not pre installed into the bearing, you need to gently press it in.
Figure 101

If the center bolt is not pre installed into the bearing, you need to gently press it in. Place an appropriately sized socket against the inner race of the bearing and then press the bolt in using a vice. Be sure that the socket only presses on the inner race of the bearing. This will assure when you press in the bearing that any force used is applied only to the inner race of the bearing. Applying force to the outside race of the bearing when pressing can damage the bearing and shorten its life. You can press in the center stud and then place the entire assembly into your freezer.

Here's the inside of the intermediate shaft, all cleaned out and ready for the installation of the new bearing.
Figure 102

Here's the inside of the intermediate shaft, all cleaned out and ready for the installation of the new bearing.

This photo shows how the new bearing and improved center stud fit into the bearing installation tool.
Figure 103

This photo shows how the new bearing and improved center stud fit into the bearing installation tool.

Install the 12mm nut on the end of the bolt to secure the bearing, the tool, and the bolt together as a single assembly.
Figure 104

Install the 12mm nut on the end of the bolt to secure the bearing, the tool, and the bolt together as a single assembly.

Use a deep socket tool to hand-tighten down the nut on the bolt and secure the assembly together.
Figure 105

Use a deep socket tool to hand-tighten down the nut on the bolt and secure the assembly together.

Nothing makes a tasty snack like some ice cream and an intermediate shaft bearing! Prior to installation, store the bearing and tool together in the freezer.
Figure 106

Nothing makes a tasty snack like some ice cream and an intermediate shaft bearing! Prior to installation, store the bearing and tool together in the freezer. This trick is commonly used with wheel bearings and shrinks the outer race just slightly when you install it, allowing you to use much less force during the installation. You want to place as little force as possible on the intermediate shaft because you don't want to knock it loose from where it's being held in place by the set screws.

With the bearing inserted into the installation tool, place it in the intermediate shaft bore.
Figure 107

With the bearing inserted into the installation tool, place it in the intermediate shaft bore.

Make sure that the tool is square (not angled) with respect to the bore.
Figure 108

Make sure that the tool is square (not angled) with respect to the bore. You want the bearing to go in straight, not cocked or at an angle. It's very important to keep this straight, otherwise you can damage the bearing when tapping it with your hammer.

Using a hammer with a plastic head, carefully tap the end of the installation tool.
Figure 109

Using a hammer with a plastic head, carefully tap the end of the installation tool. With the bearing cold from the freezer, it should not require a tremendous amount of force to install. Tap the bearing in using the tool until it's seated against the back of its bore in the intermediate shaft.

Here's the new bearing installed into the intermediate shaft.
Figure 110

Here's the new bearing installed into the intermediate shaft.

Here's the bearing shown installed in the bore of the intermediate shaft with the outer spacer in place (yellow arrow).
Figure 111

Here's the bearing shown installed in the bore of the intermediate shaft with the outer spacer in place (yellow arrow). This is an engine that used the double-row bearing.

For engines that use the double-row bearing, you install the new bearing, the spacer, and then the Spiroloc circlip.
Figure 112

For engines that use the double-row bearing, you install the new bearing, the spacer, and then the Spiroloc circlip. Thread the clip into the groove and then rotate it to install it in place.

Here's a shot of the Spiroloc clip partly installed into the groove.
Figure 113

Here's a shot of the Spiroloc clip partly installed into the groove.

If you are installing the kit on an engine with a single-row bearing, then install the circlip with circlip pliers.
Figure 114

If you are installing the kit on an engine with a single-row bearing, then install the circlip with circlip pliers.

With the bearing, the large outer spacer, and the Spiroloc installed, it's time to install the bearing cover along with the smaller spacer.
Figure 115

With the bearing, the large outer spacer, and the Spiroloc installed, it's time to install the bearing cover along with the smaller spacer. Place the small spacer on the bearing cover as shown by the yellow arrow. If you are reinstalling the bearing cover with the later-style improved seal, I recommend using a new one (part number: 996-105-112-01)

Gently tap on the new cover, working it onto the engine carefully and slowly.
Figure 116

Gently tap on the new cover, working it onto the engine carefully and slowly. I also recommend applying a thin coat of Curil-T sealant to the outer seal in order to guard against oil leaks. (double row shown)

If you're having trouble tapping in the cover into the bore of the case, you can use some M6x25mm bolts to help drive the cover into place.
Figure 117

If you're having trouble tapping in the cover into the bore of the case, you can use some M6x25mm bolts to help drive the cover into place. Once the cover is seated, then replace the longer bolts with new Torx bolts.

With the end cover in place, you can remove the set screws in preparation for installing the cover bolts.
Figure 118

With the end cover in place, you can remove the set screws in preparation for installing the cover bolts. (double row shown)

Shown here are three brand new Torx bolts from Porsche for the intermediate shaft cover.
Figure 119

Shown here are three brand new Torx bolts from Porsche for the intermediate shaft cover. The bolts are "micro-encapsulated" which is a fancy word meaning that they simply have some sealant on the threads. I like to use new bolts to assure against leaks, but you can also reuse your old bolts if you liberally coat the threads with sealant prior to installation.

Use the old bolts to tighten down the cover.
Figure 120

Use the old bolts to tighten down the cover. Then remove the old bolts and use the new bolts to tighten down the cover. Torque to a maximum of 8 ft-lbs (11 Nm). If you're not using new bolts, then be sure that you coat the threads with a liberal amount of sealant so they won't leak. With the cover in place, slide on the o-ring as shown. I recommend coating the o-ring with a thin layer of Curil-T to guard against leaks. (double row shown)

Install the spacer onto the bearing flange.
Figure 121

Install the spacer onto the bearing flange. (double row shown)

Using a screwdriver to hold the center bolt in place, tighten down the 12 point nut to to 24 ft-lbs maximum.
Figure 122

Using a screwdriver to hold the center bolt in place, tighten down the 12 point nut to to 24 ft-lbs maximum. I also like to add just a touch of Curil-T sealant between the spacer and the nut, just to make sure there is no oil leakage. (double row shown)

Here's the single-row cover installed with new Torx bolts and the shaft o-ring in place (yellow arrow).
Figure 123

Here's the single-row cover installed with new Torx bolts and the shaft o-ring in place (yellow arrow). I recommend coating the o-ring with a thin layer of Curil-T to guard against leaks.

Here's the single-row cover installed with the extended spacer in place (green arrow).
Figure 124

Here's the single-row cover installed with the extended spacer in place (green arrow).

Here's the single-row cover installed with the o-ring, spacer, and nut installed and tightened down.
Figure 125

Here's the single-row cover installed with the o-ring, spacer, and nut installed and tightened down. I also like to add just a touch of Curil-T sealant between the spacer and the nut, just to make sure there is no oil leakage.

This photo shows the LN Engineering ceramic bearing installed into the case.
Figure 126

This photo shows the LN Engineering ceramic bearing installed into the case. The engineers at LN Engineering have theorized that the removal of the seal will allow fresh motor oil to lubricate the ceramic bearing, thus they have removed the seal from the rear-facing side of the bearing.

This photo shows the LN Engineering IMS retrofit kit installed.
Figure 127

This photo shows the LN Engineering IMS retrofit kit installed. Use a small amount of Curil-T or similar flange sealant around the edge of the nut to insure against small leaks. Also remember not to reuse the old cover mounting bolts without sealant: they must either be new or coated with sealant in order to seal the holes in the case and prevent oil leakage.

On pre-2003 Boxsters and Carrera 996s, the engines all had five chains: two linking each pair of camshafts to the intermediate shaft, one linking the intermediate shaft to the crankshaft, and two linking each camshaft together.
Figure 128

On pre-2003 Boxsters and Carrera 996s, the engines all had five chains: two linking each pair of camshafts to the intermediate shaft, one linking the intermediate shaft to the crankshaft, and two linking each camshaft together. I'm not sure why Porsche designed it this way: most modern cars don't have this many chains. The good news is that on these early 5-chain cars, the timing chains almost never skip a tooth when performing the intermediate shaft bearing replacement. The chains are very tightly wrapped around each gear and as a result, when you loosen the tension from them, they tend to stay in place.

Starting in 2003, Porsche went to a 3-chain design, eliminating the chain that tied the two camshafts together.
Figure 129

Starting in 2003, Porsche went to a 3-chain design, eliminating the chain that tied the two camshafts together. I can only speculate that this was done in order to simplify the construction of the motor (reduce cost and weight). This design works fine, except that there is more opportunity now for the chain to slip off the camshaft sprockets when replacing the intermediate shaft bearing. Specifically, the chain has a tendency to slip on the 1-3 exhaust camshaft when the chain is loosened. It is for this reason that it's very important to check the engine's static timing marks on all four camshafts to make sure that the chains did not skip a tooth. If you start up the motor and the chains are off by one tooth, then the valves can impact the pistons and the engine will self destruct. It's not very difficult to check the timing: you just need to remember to do it.

Here's a photo of the later-style 9612 tool, which is similar to the P253 tool, but adjustable.
Figure 130

Here's a photo of the later-style 9612 tool, which is similar to the P253 tool, but adjustable. I believe this is used for assembly of the engine on the bench.

In order to check the timing with respect to the crankshaft, set the engine at Top Dead Center and lock it in place using the TDC tool.
Figure 131

In order to check the timing with respect to the crankshaft, set the engine at Top Dead Center and lock it in place using the TDC tool.

If you don't have the TDC tool, then a 5/16
Figure 132

If you don't have the TDC tool, then a 5/16" drill bit will work just as well for locking the engine at TDC.

At the camshaft end cover, and then you will see the end of the camshaft, along with the timing slot.
Figure 133

At the camshaft end cover, and then you will see the end of the camshaft, along with the timing slot. Check your scribes on all four camshafts for the 2003+ motors, and the scribes on the two exhaust camshafts for the 1997-2002 motors

Shown here is the P253 camshaft timing tool, which is useful for checking the timing on the pre-2003 motors.
Figure 134

Shown here is the P253 camshaft timing tool, which is useful for checking the timing on the pre-2003 motors. For 2003 and later motors use the 9686 tool to check the camshaft timing.

Shown here is the P253 camshaft timing tool installed in place.
Figure 135

Shown here is the P253 camshaft timing tool installed in place. On the 5-chain motors, the two camshafts are locked together: if one of the camshafts is still properly aligned with the crankshaft, then both of them properly timed. With the locking tool in place, you can rest assured that your camshaft timing is set properly. Check both sides, cylinders 1-3 and cylinders 4-6.

This photo shows the end of the intake and exhaust camshafts for cylinders 1-3 on the 3-chain motor.
Figure 136

This photo shows the end of the intake and exhaust camshafts for cylinders 1-3 on the 3-chain motor. Prior to removing the intermediate shaft bearing cover, you should have marked these camshafts. If you didn't mark them, you can set the motor to TDC, and then visually inspect them to make sure that they are set to the proper timing.

With the later-style 3-chain motors, the camshafts share a long chain that wraps around the outer edge of the camshaft gear.
Figure 137

With the later-style 3-chain motors, the camshafts share a long chain that wraps around the outer edge of the camshaft gear. With these motors, you must check all four camshafts to make sure they are properly timed after installing your new bearing. The 9686 camshaft locking tool is shown here in this photo, locking camshafts 1-3 on this 3-chain engine. The engine must be at Top Dead Center for the tool to fit into the pair of camshafts. If it doesn't fit, then try rotating the engine 180 degrees. With the locking tool in place, you can rest assured that your camshaft timing is set properly. Check both sides, cylinders 1-3 and cylinders 4-6.

Using a straight edge, you can line it up against the edge of the camshaft and confirm that the timing is correct (as shown in the photo).
Figure 138

Using a straight edge, you can line it up against the edge of the camshaft and confirm that the timing is correct (as shown in the photo). The Porsche camshaft tool 9686 is the preferred method of checking the camshafts, but if you don't have that tool, you can visually inspect them as shown here.

Place a new camshaft end cover onto the end of the camshaft.
Figure 139

Place a new camshaft end cover onto the end of the camshaft. Some people recommend using some Curil-T or similar flange sealant around the plugs, but these typically don't leak oil.

Tap on the camshaft end cover with a rubber mallet until it's flush with the cylinder head surface.
Figure 140

Tap on the camshaft end cover with a rubber mallet until it's flush with the cylinder head surface.

Here is the camshaft end cover shown installed flush with the cylinder head and camshaft cover.
Figure 141

Here is the camshaft end cover shown installed flush with the cylinder head and camshaft cover.

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Comments and Suggestions:
Jay Laifman Comments: Is the engine serial number different than the engine number? Here Wayne describes it as the number on the angled flat on the bottom left of the engine:
http://forums.pelicanparts.com/boxster-cayman-forum/600404-where-engine-serial-number-located.html

I got back under there and found at the very bottom, center, there are two flats, presumably of the two halves of the case. It is 13568. But that's not 8 digits either. On my angled flat spot, that Wayne identifies, I have the number I already provided: M96 / 21 67V 03360.
September 30, 2014
Jay Laifman Comments: I'm in the process of pulling my tranny to change the clutch, and will do an IMS bearing change while I've got it open. I will of course find out exactly what bearing I have when I get it out. But, in the meantime, when I look at the chart of engine numbers above to see what kind of bearing I have, they don't match the format of the engine on my car: M96 / 21 67V 03360. Am I looking at the wrong number?
September 28, 2014
  Followup from the Pelican Staff: Engine serial numbers are eight digits. On a 986 the engine number is stamped on the crankcase, at the bottom. - Nick at Pelican Parts  
Aces Comments: Hi - Can you give some guidance please?
I have a late 2005 987, and not a lot of funds so I am trying to keep this as economical as possible. First - Identifying the bearing - I think I saw somewhere a suggestion it could be seen with an endoscope without taking the transmission off - any comments? I don't really want to take off the trans just to find out I can't change the bearing
Also - If I do the work myself is it easier to drop the transmission or the whole rear end - ie engine trans, subframe ?
Thanx
September 25, 2014
  Followup from the Pelican Staff: I think you have the later bearing, that is captured inside the crankcase. - Nick at Pelican Parts  
tuan Comments: if i buy the pelican parts replacement kit, do i still need to buy the LN removal tool also?
September 13, 2014
  Followup from the Pelican Staff: Yes, you will need a puller. - Nick at Pelican Parts  
cam Comments: As stated in articlae - Why does the clutch need to be replaced every 30 - 45 k miles? Surely it should last more than this with proper driving?

Also will oil not leak from the shaft through the improved centre bolt as the olt now has no seal on it?
August 22, 2014
  Followup from the Pelican Staff: I would think if you drive easy, the clutch will last longer.

Oil will not leak once the IMS is replaced.. - Nick at Pelican Parts
 
Eric Comments: Excellent article, I just replaced my IMSB with your kit. I have a question, I used the single row spacer for the o-ring and the nut, but the nut only engages about half of the threads as shown on your how-to photos, is that sufficient? Thanks!
August 11, 2014
  Followup from the Pelican Staff: No, it should go on as shown in this photo. - Nick at Pelican Parts
GregK Comments: Hey guys.
This article on the LN engineering website seems to contradict some IMS failure rates posted. In particular it states that the double row bearings used in the 911 up until 1999 has a less than 1% failure rate, as opposed to the 8% failure rate of single row bearings.
What is your take on all this?

http://imsretrofit.com/ims-101/

Cheers,
Greg
August 6, 2014
  Followup from the Pelican Staff: LN knows there stuff. I am unsure of where the data comes from. Porsche will not release the info, maybe this is their personal experience. - Nick at Pelican Parts  
gmund1948 Comments: Nick My build date for my 2005 Boxster S is 6-2-2005 it is a 987.1 engine number 62507798 can you help me figure out if I can do an IMS upgrade I bought the car and its 1500 miles away : please advise by Email on which Ln unit to use
thanks
August 4, 2014
  Followup from the Pelican Staff: Your vehicle should have a single row. See this page http://www.pelicanparts.com/catalog/shopcart/101P/POR_101P_BOX014_pg1.htm Or Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
gmund1948 Comments: Just agreed to purchase a very early Boxster S 987.1 one of the first from the original owner, 6 speed manual used for commuting. 110K miles Clutch was done and all the records come with the car. Is there a way to tell by vin if it is replaceable? without engine tear down. I was going to do the double LN New as insurance so how do I know if it can be done externally thanks
July 31, 2014
  Followup from the Pelican Staff: What is the production date? I can help you figure it out. - Nick at Pelican Parts  
dave Comments: Going to buy a2008 cayman with 43K miles 2.7 motor does the ims issue apply? What should I check? is there a replacement part?
July 17, 2014
  Followup from the Pelican Staff: These engines can have IMS issues. The repair is a bit more complicated as the engine has to be removed and disassembled to replace it. - Nick at Pelican Parts  
Manuelle Comments: I have a Porsche Boxster 1999 with 48000 miles, do I have to this IMS?? If i do can i wait until my clutch is for replacement?
June 29, 2014
  Followup from the Pelican Staff: You do have an IMS. I would have the IMS area inspected for signs of oil leaks. Don't wait too long to replace it. - Nick at Pelican Parts  
paulo Comments: Hi Guys, I have a 2003 2.7 boxster covered 60000 in the UK, there is an intermittent rattle coming from the engine every 3-4 seconds, an independent garage have dropped the oil and stethoscope'd etc and determine a faulty IMS although it has not totally given up...it still runs and drives ok, I am not driving though. Do you think that to clean shaft, replace bearing and flush engine would be ok or shoud I go with what all the other garages that I've contacted say and go for a rebuild / replacement engine....no one is saying that it is good to replace as metal parts could be anywhere in the engine . . . . just want to know before I throw £6000 away and it could have been swapped and flushed etc As it is still running I think it could be upgraded cleaned and flushed
June 23, 2014
  Followup from the Pelican Staff: I would have the oil tested. If there is metal from the bearing in the oil, you may need a rebuild. Just flushing and replacing the bearing would likely be only a temporary band aide. - Nick at Pelican Parts  
Juan Cortes Comments: Hi, I live in Bogota Colombia and I have a 997.1 S, M97 engine , year 2005 and need to change the IMS kit, which one do you recommend for my car.
April 24, 2014
  Followup from the Pelican Staff: I like the LN Engineering kit:

- Nick at Pelican Parts
 
Marty Comments: Recently bought 2003 Box S..Tiptronic 14K miles.I'm totally naive..first Porsche. By now your kit should be available. Know any reliable experienced folks-TAcoma or Seattle..and aprox costs? Time down to fix? It's daily driver! 20 K now..changing oil this week. Great work you are doing for naives like me..thanx! Martin
April 12, 2014
  Followup from the Pelican Staff: I don't. I always suggest checking with your local PCA chapter. They an suggest a few good shops. - Nick at Pelican Parts  
bodan Comments: Hi, first thanks for your excellent articles. I would like to do an IMS Bearing Upgrade on my 2001 Boxster. I was thinking about the LN kit but then I discovered this: http://europeanpartssolution.com/products/ims-bearing-repair/
This seems to be a nice solution. What are your thougts about it and do you supply this upgrade? Thank you very much. Jakub
January 23, 2014
  Followup from the Pelican Staff: These days there seems to be more IMS bearing fixes than screenwriters in Los Angeles! I am not familiar with this particular kit or it's longevity. Until there are quite a few cars running thousands of miles with these newer kits, who knows? - Wayne at Pelican Parts  
144mph Comments: Hi, thanks for the writeup.

I performed the IMS replacement and used these instructions as a guide. However, I mistakenly thought I could either use the set screws or fix the camshafts in place with the LN tool. I only locked the cams in place. Upon reassembly, the engine idles rough and will occasionally backfire. I've visually checked the timing and it appears to be correct with the engine at TDC and then again after several 360 rotations. Engine codes show random misfire on cylinders 1,2,4 and 5. Can you suggest what the problem and corresponding solution would be?