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 > Technical Articles: / BMW E36 3-Series (1992-1999) >
BMW Rod Bearings & Oil Pump Nut Replacement
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Pelican Technical Article:

BMW Rod Bearings & Oil Pump Nut Replacement


8 hours8 hrs


$87 - $107




10mm, 11mm sockets and combination wrenches, small hammer, Isopropyl alcohol, brake cleaner and/or carb cleaner, powder-free latex gloves, Plastigage, micrometers, Liquimoly assembly lube, floor jack and two jack stands, 32mm wrench, 16mm socket, 12mm socket, ratchet

Applicable Models:

BMW E30 3-Series (1984-93)
BMW E36 3-Series (1992-99)

Parts Required:

Rod bearings and connecting rod bolts, oil pump sprocket nut

Performance Gain:

Restore power to bottom end of engine and restore performance

Complementary Modification:

Replace engine oil and oil filter
101 Performance Projects for Your BMW 3 Series

This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.

The connecting rod bearings in BMW engines transmit 100 percent of the load from combustion to the crankshaft. As a result, the bearing surfaces do not wear evenly. The side of the bearing facing opposite the piston tends to get the most wear, because the rod pushes on it with a huge amount of force when the cylinder fires. On the opposite side of the power stroke, the same rod pulls the piston and rod assembly back toward the crankshaft, creating wear on the opposite side. These push-pull forces on the crankshaft bearings are exactly opposite each other and create wear patterns on opposite sides of the bearing journals. BMW connecting rods, like the crankshaft itself, are robust parts. Rods typically become damaged when a more basic problem, like low oil pressure, caused by high heat or simply low oil levels, causes the rod bearings to run dry. The rod bearing journals are some of the last components to receive oil, and thus are often the first to run dry when the engine oil level runs low. The result is catastrophic failure, as the rod itself crushes and squeezes the rod bearings against the crankshaft.

If your engine has suffered from a loss of oil pressure, the first thing I recommend you do is replace your rod bearings. They are the one component most likely to be damaged by low oil pressure and the one component that, if worn, will result in complete engine failure. When most people think of bearings, they think of ball bearings like you would find in the wheel of a bicycle. The rod bearings are very different; they are basically a strip of curved metal that an oil film floats on. When the engine is running perfectly, the connecting rod bearing never touches the crankshaft, as thin oil molecules are suspended between the bearing and the crankshaft. The only time they might touch under normal circumstances is when you first start up the engine and there's not much oil pressure built up yet.

If your engine runs low on oil pressure, the crankshaft will ride on the actual metal bearing strip with no thin film in between. This accelerates the rod bearing wear significantly, causing the bearings to overheat and disintegrate in a matter of minutes. If the engine hasn't seized and you've driven the car with the low oil pressure lamp on for even a short while, you should bite the bullet and replace the rod bearings as soon as possible. A catastrophic drop in oil pressure might be caused by hitting a large rock on the freeway that punctures the bottom of your oil sump, or having the oil pump nut come loose on your E36 six-cylinder engine (more on this later).

Rod bearing replacement is generally straightforward. The toughest part of the procedure is getting to the bearings themselves. On the E30 and E36, this involves removing the front suspension, front axle support bar, steering rack (Project 59), and lower sump oil pan (Project 19). Once all of this equipment is out of the way, you have ready access to the rod bearings.

Begin by rotating the engine so you can reach the rod bolts. The rod bolts can be accessed in the following sequence: 1 and 6, 3 and 4, and 2 and 5. Turn the crankshaft over so each pair moves to its lowest position. Use a socket and driver on the front crankshaft pulley nut (see Photo 3 of Project 17). Remove the two rod bolts from each of the two rods, and gently pull off the rod end cap. If it sticks on the end of the rod, tap it lightly with a very small hammer. With the cap removed, gently push the other rod half up into the engine until the rod can clear the crankshaft journal. Place a small strip of cardboard against the surface of the crankshaft--you don't want to scratch the delicate polished surface of the crankshaft with the edge of the rod.

Inspect the rod bearings when you remove them. They should be a dull grey, with no indications of wear or discoloration. If they are shiny, if you see brass-colored metal, or if the bearings are missing chunks or pieces, they are surely worn and need to be replaced.

Replacement rod bearings must be matched to the crank. If you use a crankshaft that has had rod journals reground, you will have to use oversized rod bearings. Measure the rod journals on the crank before you order any replacement rod bearings.

Using a clean-room wipe and isopropyl alcohol, carefully clean each rod bearing (see Photo 4). Install each bearing into the rod cap and rod half. Depending upon which engine you have, there may be upper and lower bearing shell halves (blue for the top side and red for the lower side near the rod cap). Using a clean-room wipe and isopropyl alcohol, clean all oil and residue off of the rod bolts and nuts. Then install the new rod bolts into the cap. Apply a generous, but even, layer of assembly lube to the rod bearing. Spread the assembly lube across the rod bearing with your finger while wearing powder-free latex gloves. If you don't gloves, wash your hands first with nonpumice soft soap and make sure they are clean of any dirt or debris. Lubricate both bearing halves, and wipe a small amount around the sides of the big end of the rod to help lubricate any side contact the rod and crankshaft might see before adequate oil pressure is achieved.

Each rod is stamped with a unique number, and rods and their matching caps must be kept together. Make sure the numbers stamped in the rod butt up against each other. If you have the cap aligned correctly, with the numbers lining up, the rod bearing tangs located on the edge of each bearing will also butt up against each other. Double-check that you have properly lubed all the bearings and lined up the rods with their matching caps before you begin to torque the rod nuts to their final values.

Rod nuts and bolts are one-time-use parts designed to be tightened to their torque values only once. Always use new rod bolts and nuts when replacing your rod bearings. When tightening the rod bolts, carefully follow the torque values and use a calibrated torque wrench. Rod bolt torque values vary considerably; see for a listing of torque values and tightening procedures. Most procedures involve tightening the rod bolt to a specific torque value, and then further tightening the bolt a certain number of degrees.

With the new bearings installed, follow BMW's engine break-in instructions. Disconnect the fuel or DME relay, and allow the car to build oil pressure by turning over the starter in 10-second increments. Repeat this step at least three times to build oil pressure in the engine. Breaking in an engine involves all of the parts in the engine beginning to wear together, finding their groove. Close-tolerance parts actually wear and machine themselves into proper alignment with their counterparts over time. For the first 1,200 miles, do not exceed engine rpm of 5,500 or road speed of 105 miles per hour.

Interestingly enough, there is a factory recall notice (SI B 11 04 04) that dictates rod bearing replacement on the E46 M3 with the S54B32 engine, produced from February 12, 2001, through May 22, 2003. The original bearings in these engines were prone to failure if the engines were driven at high rpm for extended periods of time (exactly what you'd expect to do to an M3). The design of the S54 motor is very similar to the earlier inline six-cylinders, and the rod bearing replacement procedure is the same. The factory recall involves replacing the bearings and an update to the factory engine management software (DME) to restrict rpm when the car is in lower gears.

Oil pump nut

A relatively new failure mode is occurring on some six-cylinder BMW engines, like the ones used in the E36 series. The oil pump gear attaches to the engine crank by a chain and a sprocket held on with a small reverse-thread nut. There have been many recent reports of this nut coming loose and falling off the sprocket. As a result, the sprocket becomes loose and can separate from the oil pump, leading to zero oil pressure in the engine. This can be catastrophic to the rod bearings, which are typically the first components to fail.

It hasn't been determined what causes this loosening of the nut. Some people I've spoken to seem to believe the odds of it falling off may be increased by aggressive driving and go so far as to suggest it happens when the chassis of the car is spun around on the pavement (like at the race track). Whatever the cause, this very serious problem seems to be affecting many more cars as they age and are driven harder and harder. The problem doesn't seem to correlate to mileage, as many lower-mileage cars appear to have been affected as well (cars with less than 50,000miles on the odometer).

To solve this problem, remove the lower oil pan and secure the nut in place so that it will not fall out. The one fail-safe trick to secure the nut is to tack weld it to the sprocket. Once welded, that nut is not going to come off under almost any circumstance. Other people have run safety wire through the nut, applied Loctite, and deformed the inner edge of the nut with a punch. If you don't weld it, at least replace the nut with a new one (part number 11-41-1-735-137). Keep in mind that this nut is reverse threaded, so to remove it, you need to turn it clockwise.

If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.

Figure 1

A complete rod bearing replacement kit for a four-cylinder 318i contains eight bearing shells, eight rod bolts, and eight rod nuts. Don't ever reuse rod bolts--they are stretch bolts and are only designed to be tightened once. Be sure to purchase the correct size rod bearings, as they need to match the size of your crankshaft (see Photo 3).

Figure 2

You can access the rod bearings relatively easily after you remove a bunch of other items (front axle support bar, steering rack, lower oil pan cover). Although it may seem difficult to reach the rod bearings, having access to them in this manner means that you won't have to remove the engine and tear it down as on many other cars. This is a view of the crankshaft and connecting rods from underneath the engine. The red arrow points to a rod nut. The yellow arrow indicates the back side of a piston. The green arrow shows a bolt that holds a cap for the crankshaft bearings. The blue arrow on the left shows the engine flywheel. The purple arrow points to the bottom half of the engine oil dip stick. Crankshafts are marked with various colored paint, depending upon tolerances (in this case a red mark, shown here by the orange arrow).

Figure 3

If you remove the crankshaft from the car, you have the luxury of using a regular-sized micrometer to measure the rod bearing journals. If maneuvering inside the lower part of the BMW engine, you may have to experiment with various micrometers and dial calipers in order to measure the journals accurately.

Figure 4

Perhaps the most important task in the assembly process may very well be proper cleaning. Clean as much of the rod and bearing cap as possible with brake or carburetor cleaner. Gently wipe the surface of the bearing with a clean-room wipe and alcohol, and also wipe the bearing journal of the rod. Wipe down the crankshaft rod bearing surface, and double-check that there is no dirt anywhere on the assembly.

Figure 5

Use Plastigage to measure the clearance between the rod bearing and the crankshaft. Lay the wax out across the bearing surface as shown here. After tightening the rod nuts and bolts to their final torque values (using only old rod bolts and nuts), the wax will flatten out. Compare the width of the wax to the measurement scale enclosed with the Plastigage to obtain an accurate reading of the clearances. For most engines, the specified value should read between 0.020 and 0.055 millimeter.

Figure 6

Wearing a powder-free latex glove, use your finger to gently spread a thin layer of assembly lube on the inside surface of each bearing. Don't gob it on, but spread it evenly across the bearing surface. I prefer to use LiquiMoly assembly lube, as it doesn't run as much as others I've tried.

Figure 7

Don't mix and match the rod end caps. There are numbers stamped on them to keep them properly oriented with respect to the rods. The edges with numbers on them should line up when bolting the rods together. The rods in your BMW engine may vary slightly from those shown here.

Figure 8

Here's a close-up shot of the underside of the piston (yellow arrow). The blue arrow shows the connecting rod. On the side of the rod there should be a paint mark indicating which size bearing fits the rod. The inset shows a worn-out rod bearing. This bearing was run in an engine that ran low on oil pressure. As a result, the crank and bearings rode on each other, resulting in significant wear as the crank and bearings experienced direct metal-to-metal contact. Inset: Jacques Weingartz

Figure 9

The dreaded oil pump nut (red arrow) is a reverse-thread nut known to back out unexpectedly, resulting in the sprocket falling off of the oil pump shaft. This will cause an immediate drop in oil pressure and quite possibly complete destruction of the engine. Tack weld the nut to the sprocket so it won't fall off. You can always use a Dremel tool later on if you need to replace the sprocket or the chain. The upper inset photo shows the splined shaft of the oil pump that the sprocket mates to. The lower inset photo shows the inside teeth of the sprocket. The nut may be loose and the car will run fine for thousands of miles, as the chain tends to keep the sprocket roughly in place on the oil pump shaft.

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Comments and Suggestions:
mos Comments: Thanks Nick for your respond, my question then will be if the chain is too loose , what need to be done because i am suspecting that the noise is coming from the same chain , i have replaced vanos and top chain and the primary tentioner. so what happens is, when i rev the car it makes the grinding noise @ 3.5rpm
September 13, 2016
  Followup from the Pelican Staff: Check if the pulleys are worn down, look for points or sharper teeth on the sprocket. - Nick at Pelican Parts  
mos Comments: how adjust oil pump chain tention for bmw e36 328i m50.

thanks and regards
September 12, 2016
  Followup from the Pelican Staff: There is no tension adjustment. The chain is installed along with the sprocket. Only the main timing chain uses a tensioner. - Nick at Pelican Parts  
z Comments: What is the Torque Spec for the Oil Pump Nut?
March 27, 2016
  Followup from the Pelican Staff: I don’t have that info.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
mick Comments: Hi I drive a e36 bmw 325i.will the 328i e36 camb blocks and lifters work on my 325i?thanks for all your help really appriciated.
August 29, 2015
  Followup from the Pelican Staff: The cam locking set should work the same on both of those vehicles. - Nick at Pelican Parts  
gles Comments: Hi guys...I have E36 328i machine..its smoking and showing white smoke at start and its gets a bit black when I increase speed. But there'sa lot of oil in the tthrottle body. So I am stuck. I changed the oil separator together with the valve but still smokes.
February 15, 2015
  Followup from the Pelican Staff: Could be oil residue. Try cleaning the oil out of the intake manifold. The the smoke doesn't go away, you may have a faulty engine seal or rings. - Nick at Pelican Parts  
gles Comments: Hi guys...great job u r doing....what is the oil pressure range or spec for e36 328i
February 1, 2015
  Followup from the Pelican Staff: idle is about 7 psi, regulated oil pressure (engine RPM about 2500) 59 psi- Nick at Pelican Parts  
ShawnB Comments: My internet was acting up, so there might be 2 of the same message, sorry. 1. I plan to replace my crank and piston bearings in my 02 BMW 325i, and would like to get my crank turned down. Any advice, or really you just can't go wrong and do it.I will be buying the Bentley repair manual, but might take my crank in to get turned before I buy it, then study the hell out of it, while waiting on crank.
2. What are the key things I need to know or have ready when contacting the machine shop, to tell them what I want. or, do they look that info you them selves, by looking up bearing sizes available for the engine, and turn it down for the next bearing size. etc....
August 29, 2014
  Followup from the Pelican Staff: I would check with parts for bearing kits, you will have to plastigauge the crank to determine bearing thickness. As far as turning the crank, if it is damaged, you may be better off with a replacement. Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
ShawnB Comments: 1. I plan to replace my crank and piston bearings in my 02 BMW 325i, and would like to get my crank turned down. Any advice, or really you just can't go wrong and do it.I will be buying the Bentley repair manual, but might take my crank in to get turned before I buy it, then study the hell out of it, while waiting on crank.
2. What are the key things I need to know or have ready when contacting the machine shop, to tell them what I want. or, do they look that info you them selves, by looking up bearing sizes available for the engine, and turn it down for the next bearing size. etc....
August 29, 2014
  Followup from the Pelican Staff: I answered you under your other question. - Nick at Pelican Parts  
M3 Power Hustle Comments: Great job Guys. great write-up. I have a question about the dreaded oil pump sprocket nut. I stripped the nut off being an idiot and not knowing it was reverse threaded. I had to cut the nut off...but I'm worried the threads on the bolt might be too damaged. Is it possible to replace the bolt as well without replacing its housing components of the oil pump entirely? Thanks guys.
July 30, 2014
  Followup from the Pelican Staff: I don't believe so. Unless you can find a rebuilder. I am pretty sure the parts are not separately. - Nick at Pelican Parts  
C LIVE Comments: Yes Nick the engine fan indies nolonge turn in the time off need it turns fulltime,I have changed fan,fanswitch, relay for fan, temperature switch still is still running ws working normal all this time please help.
July 17, 2014
  Followup from the Pelican Staff: I would check if the coolant temp sensor circuit is open. If it is, the DME will turn the fan on. CHeck the signal to the DME. - Nick at Pelican Parts  
C LIVE Comments: Bmw 318i m43 e46 2001 model is turning fan little while after u have started the car,changed the fan switch still it will stop when u turn ignition off please help
July 15, 2014
  Followup from the Pelican Staff: I don't follow. The fan as in engine fan? The engine cooling fan will only come as needed. It does not run all the time. - Nick at Pelican Parts  
brandon Comments: Hi guys I have a bmw E36 M43 318is the piston
Hit the block so I repaired my block bt now I want to know
If it is a must to replace my oil pump kit some valve also bend
June 8, 2014
  Followup from the Pelican Staff: If there was a failure that put foreign object debris into the engine, would replace the oil pump. - Nick at Pelican Parts  
Sihle Mavimbela Comments: Hi guys I where can I get the books with info and engine specs on BMW's
April 19, 2014
  Followup from the Pelican Staff: try this link: =20&GoSearch_side=GO&GoSearchSideFlag=&command=DWsearch&command=DWsearch&REFINE=Y&FORUM_REFER=&SUPERCAT_FLAG=Y&Previous_Section=&LastVisited_input=&make=BMW&description=books+&FILTER_ALL_MAKE_BMW=books - Nick at Pelican Parts
C LIVE Comments: Hi guys my bmw e46 318I M43 engen smell carbon or sosomething like burning oil,I checked everywhere there is no burning oil what could it be pls help and also smelling petrol after driving long distance
April 10, 2014
  Followup from the Pelican Staff: I would inspect the engine from below. the oil may not be reaching the ground. It could be the valve cover gasket dripping onto the exhaust. - Nick at Pelican Parts  
C LIVE Comments: hey guys I need help how to set my speed and my revs on the same phase or level on bmw E46 318I m43,because my revs leave my speed behind pls help
April 7, 2014
  Followup from the Pelican Staff: I don't understand the question. Is your clutch slipping? - Nick at Pelican Parts  
C LIVE Comments: Hi guys I need help on my bmw m43 318I E46,short way to replace oilpump kit
April 4, 2014
  Followup from the Pelican Staff: There isn't one. Have to drop the oil pan. - Nick at Pelican Parts  
dekelley1 Comments: Hello, I have a 2001 330ci which recently started having a low end knock that's what is sounds likeCould this just be a bad bearing? Once I get in there what would indicators should I look for concerning issues past just the bearing?

I have a video up on youtube if you could take a listen I would really appreciate it.
December 3, 2013
  Followup from the Pelican Staff: This could be a rod knock, does sound like a bad bearing. When you inspect the bearings, look for a shiny section, that would indicate a failure. You could try a bearing, but with the labor and cost involved, most people replace the engine instead. - Nick at Pelican Parts  
hank Comments: So on a 1976 2002 engine would the rod bearing tangs be on the same side as the article says for the 3 series engine? this would be in case i could not see the stamped in numbers because the rod is pretty dark and varnished. thanks
May 3, 2013
  Followup from the Pelican Staff: I'm not 100% sure on the 2002 engine. I would clean all the stains from the rods before reassembling. If there are markings you'll have a better chance of seeing them. - Nick at Pelican Parts  
will Comments: i was wondering how difficult it was to access the oil pump nut. is it simply taking the oil pan off and there it is or is there more. i have an e36 m3 1998 if it makes a difference.
March 9, 2013
  Followup from the Pelican Staff: The oil pump is in the front timing cover. You'll have to remove the lower timing cover to service it. - Nick at Pelican Parts  
don x5 Comments: my Indy did work on my bmw x5 4.6is,he replaced the oil housing cover, I drove the car, there was a ticking noise from the engine when I got home, found out that the oil pump was clogged.
he siad he fix the problem,now the engine makes a whinning noise, that comes and goes, it souds like it is coming from the oil fliter................
is it time to replace this engine? I had it rebuilt last only has 6700 miles on it?
March 11, 2012
  Followup from the Pelican Staff: The engine should last more than 6700 mi, unless there was damage done by the clogged oil pump pickup, check the oil pressure with a gauge and see it it is low, try to pinpoint where the noise is coming from.
- Nick at Pelican Parts
Chris84 Comments: Hello much pounds of torque should I set my connecting rod and also the main bearings inside the engine block on my BMW 1984 325e.pls help
April 6, 2011
  Followup from the Pelican Staff: This information is contained in the Bentley E30 workshop manual, I would suggest picking up a copy to make sure you have the right values. See page 64 - there is a whole tightening procedure that must be followed. - Wayne at Pelican Parts  
watto Comments: Great article, I'm about to change the sump gasket on my 2002 x5 3.0. Do you know if my engine has this issue with the oil pump nut and is there any other preventative suggestions that you recommend. Any help would be appreciated. Thanks
February 15, 2011
  Followup from the Pelican Staff: I think that yes, this engine does have the similar oil pump nut as the earlier cars. With a a big SUV that doesn't see much performance driving, I would think the issue is less of a concern though. - Wayne at Pelican Parts  
peewee Comments: Great article! But can you tell me the torque value for the bolts from a e30 325 engine? Cause the link doesn't include the values yet....
Thanks a lot already,
Peter Brondijk, the Netherlands
September 27, 2009
  Followup from the Pelican Staff: I don't have them handy, but this information is in the E30 Bentley manual, which you should have a copy of if you're rebuilding your engine. - Wayne at Pelican Parts  

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