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Pelican Technical Article:

Porsche Boxster / 996 Engine Teardown & Disassembly
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Difficulty Level: 4
Difficulty scale: Adding air to your tires is level one
Rebuilding a Porsche Motor is level ten

  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. 
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Figure 1
Here's the long block as we delivered it to Callas Rennsport.  We were working at Callas' shop today because we're all working together to learn as much as possible about these motors.  For the past 10 years, Porsche has offered an engine exchange program where you have to give back your old engine to Porsche when you get your replacement (known as a CORE charge).  This means that very few of these engines have been floating around for people to disassemble, as we are doing here.
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Figure 2
Under this cover lies the trouble with a lot of these engines - the intermediate shaft bearing (IMS bearing).  This bearing, when it fails, causes the engine's chains to jump off of their camshaft sprockets, and then nasty things happen (valves hit pistons, rods bend, etc.).  The bearing is a sealed roller bearing, which is odd to use in an oil-based engine.  Most bearings used in engines are lubricated by oil.  It is my opinion that the design and use of this bearing in this application was an inappropriate and ineffective design.  More on this later...
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Figure 3
There's a new fix available for this bearing.  Fortunately, you *can* replace the bearing with the engine still in the car.  I hope that most people will replace it when they perform a clutch replacement, as it's very easy to get to.  The first step is to loosen the chain tensioners that push the chains against the intermediate shaft sprockets.  This photo shows one of the main tensioners, that keeps tension on the chain that connects the intermediate shaft to the crankshaft.
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Figure 4
Loosen up the chain tensioner, but don't remove it from the case.  You want to keep a little bit of tension on the chain so that it stays in place, and you don't skip a tooth on the sprockets and lose timing on your engine.  If this happens, then you need to retime the camshafts.
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Figure 5
Here's a shot of the tensioner loosened, but not removed.  One or two threads are still holding it into the case.  You should loosen your tensioner up to about this point.  Since we will be removing the main bearing holding the intermediate shaft into place, then the shaft will float around if there's a lot of tension from the chains pulling it in two directions (up and to the side).
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Figure 6
To the right of the intermediate shaft, there is the tensioner for cylinder bank 1-3.  In the same manner as the main tensioner, loosen this one up a bit, but do not remove it from the case.  If you accidentally take it out, then you might have to retime your camshafts later on - carefully keep a little bit of tension on it at all times.
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Figure 7
   Here's another shot of the tensioner for cylinders 1-3 being loosened up.  You don't have to loosen up the tensioner for the intermediate shaft for cylinder bank 4-6.  This tensioner is on the opposite side of the engine, and the shaft will be held into place by the bearing located on the other side.  Ironically, the bearing on the other side of the intermediate shaft is not a sealed roller bearing, but a oil-based bearing very similar to the ones used in the intermediate shafts on the air cooled 911s.  I'm not quite sure why they used an apparently good design on one and and not the other.  Perhaps there was not an adequate oil supply for the area where the sealed bearing was used.
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Figure 8
The next step is to remove the intermediate shaft end plate.  You can use a simple set of mini-crow bars to pry the cover off once you remove the three nuts that hold it on.  On the early engines, these covers used to leak quite a bit, so Porsche developed an update for them.  Part number 996-105-017-02 is used for engines with the double-row bearing, and 996-105-024-01 is used for engines with the single row bearing (more on this later).  Use the following table to determine if your engine uses a single or double row:
 
Boxster Double Row:
   Engine Number up to 651 12851 (M96.22)
   Engine Number up to 671 11237 (M96.21)
 
Boxster Single Row:
   Engine Number from 651 12852 (M96.22)
   Engine Number from 671 11238 (M96.21)
 
996 Double Row:
   Engine Number  up to 661 14164
 
996 Single Row:
   Engine Number from 661 14165

 

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Figure 9
Like everything else with Porsches, there is a special factory tool for removal of the intermediate shaft cover.  I think it's complete overkill, but it's very expensive, and pretty cool.
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Figure 10
This photo shows removal of the IMS (Intermediate Shaft) end plate/cover with the special Porsche tool.
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Figure 11
Here's a view of the backside of the IMS cover.
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Figure 12
Shown here is the infamous intermediate shaft bearing.  As you can see, it's a simple ball bearing with a typical rubber seal on the outside (similar in nature to wheel bearings).  I cannot think of another engine that uses these bearings inside an oil based compartment.  The problem is that the seals that are on these bearings are not necessarily intended to be used in an oil-based environment.  What happens is that oil gets past the bearing seal, and then gets inside the bearing.  Normally, the bearing is self-lubricated, meaning that it has it's own grease installed inside of it when it comes from the factory.  But, oil from the engine gets inside the bearing after some use.  This oil tends to get stuck in there and get oil and dirty (no method to change it).  This apparently is what contributes to the premature failure of the bearing.
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Figure 13
A typical sealed ball bearing like this one is usually found in things like machinery or copy machines, that are operated in a dusty or dirty environment.  They are not typically found within oil-lubricated engines.  As such, I recommend that you remove the seal from the end of the bearing.  Charles Navarro of LN Engineering has done extensive analysis of torn apart engines, and he has repeatedly found that the bearing inside the engine becomes easily contaminated with old and dirty oil.  Removing the seal allows fresh oil to circulate somewhat within the bearing.  From the engine teardowns it has been determined that oil gets into the bearing anyways - it might as well be fresh oil.
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Figure 14
This photo shows me removing the "dust seal" from the ball bearing.
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Figure 15
Here's a photo of the bearing with the seal removed.  The seal does not hold the balls in place - that job is performed by the bearing race.  Removing the seal does not compromise the integrity of the bearing.  In this particular engine, the intermediate shaft bearing did not appear to be damaged or worn.  Something else entirely contributed to the demise of this engine.
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Figure 16
Here's another shot of the intermediate shaft bearing.  The small bolt in the center can be tapped through to the center of the shaft (see next photo).  Porsche had problems with this bolt breaking when people over-tightened them.  In the past, if the bolt broke, then you needed to tear down the entire engine to get it out.  Nowadays, we have developed a procedure (pioneered by Scott Slauson of Softronic) that allows you to remove and replace both the sealed bearing and the intermediate shaft bearing.  As of April 2009, there are two bearing kits available on the market.  One replaces the bearing with a similar one manufactured by the same company that made the original bearings used in the engine.  The kit comes complete with the improved Porsche backing plate and a new bearing with spacer (if required).  Retail for this kit is about $100.  The other kit has been developed by LN Engineering and uses a special ceramic coated bearing and custom-manufactured end cover.  This "improved design" replacement retails for about $600.
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Figure 17
If you happen to tap the bolt into the recess of the intermediate shaft, simply use a magnetic tool to pick it out.
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Figure 18
We first tried using a standard bearing puller to remove the double-row intermediate shaft bearing.  Unfortunately, we quickly broke our tool, and then had to order another beefier one that was better suited for the job.  As such, we put the removal of the intermediate shaft bearing aside, and concentrated on the removal and teardown of the heads and camshaft housings.
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Comments and Suggestions:
RYANO Comments: thanks nick,carried out test and have a u/s air oil separator.
February 19, 2014
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it.
- Nick at Pelican Parts
 
RYANO Comments: I HAVE 1998 2.5LTR BOXSTER.ENGINE HAS A SQUELLING NOISE COMING FROM THE FRONT OF THE ENGINE.I REMOVED THE DRIVE BELT AND THE NOISE WAS STILL THERE.REMOVED CRANK PULLEY AND LOCATED NOISE TO BE FRONT CRANK SEAL,SPRAYYED THE SEAL WITH THE ENGINE RUNNING AND THE NOISE WENT AWAY.REPLACED THE SEAL AND AFTER A LONG DRIVE THE NOISE CAME BACK..PLEASE HELP
February 16, 2014
  Followup from the Pelican Staff: DOes it sound like air is being drawn into the seal? You could have excessive crankcase vacuum, causing an air leak at seal. - Nick at Pelican Parts  
malkyboy Comments: Re: intermidiat shaft bearing, is it possible for cog to slip on end of shaft.somthing sliped ,timming out12 bent exhaust valves.but on investigation of int -bearing no visible signs of wear.????

January 15, 2014
  Followup from the Pelican Staff: The chain can jump timing during he procedure if not locked down properly. - Nick at Pelican Parts  
Swampy Comments: This just might save the day for all you people with broken timing chainintermidiate shaft to cam shaft you can purchase a split link for chain.similar to motor bike chain.you need to remove one link knock out pins put in new link. Ps.dont forget to feed chain over inter cog first.
November 24, 2012
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it. - Nick at Pelican Parts  
Swampy Comments: My boxster 3.2 stopped engine Jamed. Engine taken out .posible debri from previous ims change Jamed up the scavenger oil pump causing timing chain to break.is it possible to replace chain without total strip down,!,
November 8, 2012
  Followup from the Pelican Staff: I used your answer as it seems you worked it out:

"This just might save the day for all you people with broken timing chainintermidiate shaft to cam shaft you can purchase a split link for chain. similar to motor bike chain. you need to remove one link knock out pins put in new link. Ps. dont forget to feed chain over inter cog first." - Nick at Pelican Parts
 
Dennis Comments: I am looking for information on removing a Boxster 2.5 head. Do I remove the cam sprocket4 boltsor try to slip the cam chain over the end?
June 26, 2012
  Followup from the Pelican Staff: I don't think I've ever tried to remove the chain without taking off the sprocket. I don't think it's possible. I'll copy this question to the forums, and see if anyone there might know... - Wayne at Pelican Parts  
H997 Comments: Hi,
Great site!!

My car has the M97 engine with the unserviceable IMS bearing unless a teardown. To avoid any problem and prolong its live, should I remove the plastic cover on the IMS bearing to provide better lubrication. The can be done when the IMS flange is removed.
Thanks
February 16, 2012
  Followup from the Pelican Staff: I've heard of some poeple doing that. I would check with yuor Porsche mechanic and see what they have to say about it. - Nick at Pelican Parts  
art Comments: I have to much base vacum what causes that.
December 21, 2011
  Followup from the Pelican Staff: Too much vacuum in the crankcase is very often caused by a failed air-oil separator. You can find my article on the replacement of this here: http://www.pelicanparts.com/techarticles/Boxster_Tech/09-ENGINE-Air_Oil_Separator/09-ENGINE-Air_Oil_Separator.htm - Wayne at Pelican Parts  
Dave Alford Comments: I am thinking about a Boxster/Cayman. I ordered your book a week ago. Looks like I should read it cover to cover before I shop for a car!
October 20, 2011
  Followup from the Pelican Staff: Indeed, that's not a bad idea. It will help you avoid problem cars! - Wayne at Pelican Parts  
scotty Comments: i have 99 boxster the engine locked up after driving . I hear something snap when i tryed to start it . I rolled car back and forth then it started but sounded like hell. I turned it off. sence then i changed intermediate shaft bearing and still sounds bad. Now have taken engine out and timeing chain on drivers side is loose . what to do and what is best manuel for job?
April 11, 2011
  Followup from the Pelican Staff: Yikes, that sounds like a challenge! I'm going to copy your question to our forms, and then we can help you there with some suggestions. Here's the link: http://forums.pelicanparts.com/boxster-cayman-forum/603734-massive-engine-problems.html- Wayne at Pelican Parts  
Doctor Comments: How do you identify a malfunctioning intermediate shaft before a castasrophe occurs? I have a 2004 996 C4S. Hopefully not an expensive undertaking.....Thanks
November 23, 2010
  Followup from the Pelican Staff: Well, it's tough. There are a few ways to try to do it, and I've documented them in my intermediate shaft replacement article shown here: http://www.pelicanparts.com/techarticles/Boxster_Tech/14-ENGINE-Intermediate_Shaft_Bearing/14-ENGINE-Intermediate_Shaft_Bearing.htm - Wayne at Pelican Parts  
gusnina Comments: where is the engine number in a 2002 boxster 2.7L?
March 29, 2010
  Followup from the Pelican Staff: It's located on the bottom of the engine, on the side, right above the oil pan. I have some photos here:

http://www.101projects.com/Boxster/Projects/011/images/Pic700.jpg

http://www.101projects.com/Boxster/Projects/011/images/Pic698.jpg

- Wayne at Pelican Parts
 
boxhead Comments: I am familiar with the LNE retrofit kit, however it's too expensive for me. Could you please post the company of the other kit which sells for $100. Thanks!
January 30, 2010
  Followup from the Pelican Staff: Pelican is developing the kit, and it will retail for somewhere between $150 and $200. We hope to have these in stock in the very near future. - Wayne at Pelican Parts  
longislander1 Comments: I have a Boxster S built in late 2005 and am trying to find out if it has the single-row or double-row bearing. How can I find the engine number without removing the engine cover? Is the engine number in another place on the car? Thanks.
January 29, 2010
  Followup from the Pelican Staff: I have soem guidelines on how to tell which bearing is in your engine in my article here: http://www.pelicanparts.com/techarticles/Boxster_Tech/14-ENGINE-Intermediate_Shaft_Bearing/14-ENGINE-Intermediate_Shaft_Bearing.htm The bottomline is that you cannot definitively tell until you have the engine apart, unfortunately. - Wayne at Pelican Parts  
Jim Hughes nicknamed Comments: Great info. on your site. Can you help me identify what engine is installed in a 1999 Porsche Carrera 996 I just purchased. The engine number is #M96/04AT66465028. Is it a 3.4L or a 3.6L? Any help is appreciated.
July 15, 2009
  Followup from the Pelican Staff: All the 1999 cars had cable-throttle 3.4L engines. I just put one of these engines into my 2000 Boxster! - Wayne at Pelican Parts  

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