Lower cam chain tensioner DIY E36 M3

[CRYPTiC]

Just recently, I noticed a rattle coming from the front of the engine when letting off the throttle. It wasn't bad enough to notice from the driver's seat, but definitely audible when the hood is up and the throttle is actuated manually. A quick search of the forums lead me to suspect the VANOS unit, but the Pelican Parts write-up points out the possibility of a less expensive problem: lower cam chain tensioner.

I recently discovered a VANOS repair solution from DrVanos (ceegeezM3 here on bf.c) after reading this thread. The videos on the DrVanos site makes it clear what VANOS rattle sounds like. My noise, on the other hand, sounds like a metal chain being pulled over something. Kind of had to put it into words, but if you've ever lubed the drive chain on a motorcycle where the swing arm has a plastic chain guide (e.g. Ninja 250R), you'll be familiar with what I'm talking about. In my case, replacing the tensioner eliminated the noise, so here's a write-up for anyone else who wants to go this route. R&R is very straightforward.

Tools

• 32mm deep-wall socket
• Torque wrench
• Towels

A word about sockets: The only 32mm socket I could find was at Sears and it was not deep-walled. In fact, it couldn't even reach past the housing of the old-style tensioner on my S50 engine, so I resorted to a Craftsman 32mm combination wrench I originally bought to use on the fan clutch. The Sears socket, however, was just deep enough to reach over the smaller housing of the upgraded replacement tensioner and touch part of the hex head, so I was able to torque the tensioner to spec that way. Afterwards, I discovered that AutoZone has a 1-1/4" deep socket (1-1/4"=31.75mm, which is 0.25mm too small, but not enough to matter) that completely fits over the upgraded tensioner. I can't verify fit with the the old tensioner, but I'm pretty certain it could work.

PARTS

M50/S50:

• 11-31-1-405-081 (Tensioner)
• 07-11-9-963-418 (Gasket ring)

M52/S52:

• (see below)

If you have an M50/S50 engine with the original tensioner, the tensioner will basically be three pieces: an outer housing with a removable cap, a spring, and a forked piston that pushes against the chain guide inside the engine. Make sure to replace that with part 11-31-1-405-081, which is the upgraded tensioner, and a replacement washer/gasket ring. A quick look on realoem.com shows that the S52 uses a different tensioner that I can't verify. In any case, use the tensioner appropriate for your model year.

1. Preparation

First, let the engine cool down because you'll be getting very close to a part that doesn't get much direct ventilation if, like me, you did the FDM.

Second, locate the tensioner. It's on the passenger side of the engine, towards the front, above the AC compressor. Really had to miss. Place a towel on the area under the tensioner and shape it like a cup. Not a lot of oil will come out, but more than a few drops, so be prepared.

2. Removal

Remove the tensioner with a deep-wall 32mm socket. The problem here is that the body tensioner sticks out very far from the hex portion. Regular sockets may give you enough reach, but a deep socket will do the job better. A 32mm wrench works, too, if you have one from working on the fan. You'll need to use it at a bit of an angle, though. If you have clearance issues, unplug and relocate the washer fluid reservoir and/or the electrical connections to the AC compressor.

3. Reinstallation

Install the new tensioner, being sure to align the tensioner piston with the chain guide. You can use your finger to get a feel (literally) for how the piston should be oriented. A slightly more fool-proof method is to push the tensioner against the opening and rotate counter-clockwise a few times. This will allow the tensioner piston to rotate into place without applying any pressure that could lock it out of alignment. Rotate clockwise to install, of course, and torque to 30 lb-ft for S50 engines.

4. Clean-up

Lastly, put back the washer fluid reservoir and/or any connections you took out. Then fire the engine up to see how everything turned out.

[sirius600]

umm......nice write up, but you haven't told us if it solved your problem or not.

[CRYPTiC]

You read too fast. Second paragraph, second to last sentence:

In my case, replacing the tensioner eliminated the noise, so here's a write-up for anyone else who wants to go this route.

[sirius600]

Ohh, right, good job then

[M3zie]

Nice man, thanks for the write-up. I always appreciate when people post descriptive DIY write-ups, whether I need to do it yet or not. I know I'll probably be doing it some day.

[Balthazarr]

37 ft-lbs for S50
30 ft-llbs for S52

[CRYPTiC]

Do you know if there was a tensioner change for the S52 engines? Doesn't look like it in the ETK, but the ETK has mislead me before ...

[Balthazarr]

Do you know if there was a tensioner change for the S52 engines? Doesn't look like it in the ETK, but the ETK has mislead me before ...

There is a diy...somewhere. I think it was E30technic or something like that and clearly showed the breakdown of euro and US tensioner use.
I remember that the S52 was considered the upgrade for the S50.
I bought the same part as you with the one piece housing and dbl piston, but I think the S52 part had a different number.
In fact, I think I covered this in someone else's thread. I just can't remember whose.

[Balthazarr]

[CRYPTiC]

Interesting! In the case the image goes down and to aid the search engine:

E36 M3 3.0L
Euro: 11-31-1-307-782
US: 11-31-1-405-081

E36 M3 3.2L
Euro (up to 1/96): 11-31-1-307-782
Euro (after 1/96): 11-31-1-405-081
US: 11-31-1-404-438

FWIW, the Pelican Parts write-up says to use 30 lb-ft on the -081 part on S50 engines, whereas 37 lb-ft is indicated for the older multi-piece tensioner. I'll double check with the Bentley tonight.

[Toddlovesm3s]

I'm also getting that rattle noise you described and am wondering if I have the same problem. Is there a way to tell if the tensioner is bad without replacing it?

[CRYPTiC]

Not that I know of. I don't have anything to measure the spring rates of the old and new tensioners, nor are there any specs for what they should be, so I can't give you any hard metrics for comparison. Besides, I'm fairly certain the tensioners are hydraulic, so getting a measurement would be tricky regardless.

I took a gamble on it. Since my engine looks like it's had the original tensioner for 12+ years, I counted it as a wear item. Bimmerworld has them for about $100 shipped. Pelican Parts wanted $170.

[Balthazarr]

I'm also getting that rattle noise you described and am wondering if I have the same problem. Is there a way to tell if the tensioner is bad without replacing it?

I think if you have the older style, you can put a spacer ie washer at the outer end-cap-to increase tension on the spring.
I think I advised another member to do this and it worked for him.

[Balthazarr]

I took a gamble on it. Since my engine looks like it's had the original tensioner for 12+ years, I counted it as a wear item. Bimmerworld has them for about $100 shipped. Pelican Parts wanted $170.

That has to be mistake on the pelican site.
I paid $92 for mine from them in January of this year.

[CRYPTiC]

That has to be mistake on the pelican site.
I paid $92 for mine from them in January of this year.

Hope so.

http://www.pelicanparts.com/cgi-bin/...-1-405-081-M40

[Toddlovesm3s]

I really have no idea which tensioner I have, but would assume that I have the -675 part since mine is a 99 and I'm pretty sure this is the factory original. Is this the one you are talking about? If so I might give this a shot since its a cheap way to find out if thats my problem.

Mine only makes the noise when I first start driving and goes away after 15-30 seconds. I've been driving on it for a while without any major issues, but I think my car is running slightly rich from inspecting my plugs and the excessive detonating in my exhaust. Do you think the lack of tension in the camshaft chain could have anything to do with this?? Sorry for my lack of understanding on timing chains

[CRYPTiC]

That's odd ... 11-31-7-838-675 isn't in realoem.com, but the -438 part is.

I'm no engine expert either, but I'd think running rich is independent of cam timing. In any case, a VANOS fix costs at least twice as much as a new tensioner. If you're going to try new parts, I'd try the tensioner first. A good mechanic (independent or otherwise), however, might be be able swap in a spare they have tell you whether you really need a new part. Check http://bimrs.org/ if you want to find a good local indie.

[Balthazarr]

I really have no idea which tensioner I have, but would assume that I have the -675 part since mine is a 99 and I'm pretty sure this is the factory original. Is this the one you are talking about? If so I might give this a shot since its a cheap way to find out if thats my problem.

Mine only makes the noise when I first start driving and goes away after 15-30 seconds. I've been driving on it for a while without any major issues, but I think my car is running slightly rich from inspecting my plugs and the excessive detonating in my exhaust. Do you think the lack of tension in the camshaft chain could have anything to do with this?? Sorry for my lack of understanding on timing chains

Do this: take a pic and post so we can see if we can id it or remove and see if there is a spring between the piston and the housing.
If the latter, you can shim it.
If it relies on oil pressure to pump it up, you have a later version and most likely won't be able to shim the inside of piston where the spring resides.
What weight oil are you using?

[M13]

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[Casebrius]

One not on installing the new style tensioner - DO NOT push in the piston to "test" the spring. It has an internal circlip that stays locked farther down in the cylinder once pushed in. This is not good because you can't rotate the tensioner to make sure its lined up right inside on the chain guide. When I got mine, the first thing I did was to push the cylinder in to test it. Wrong move.

[erock///m3]

can you upgrade to the newer style?

[CRYPTiC]

can you upgrade to the newer style?

I did.

[mpower510]

One not on installing the new style tensioner - DO NOT push in the piston to "test" the spring. It has an internal circlip that stays locked farther down in the cylinder once pushed in. This is not good because you can't rotate the tensioner to make sure its lined up right inside on the chain guide. When I got mine, the first thing I did was to push the cylinder in to test it. Wrong move.

OMG! i just got mine and that is what i did! what do i do now?

[BlackBMWs]

I realize this is an older thread, but just wanted to check here on replacing an older style tensioner with the upgraded one.

Original one on the left, upgraded one on the right. Can anyone else who made this swap please confirm that this looks like the right upgraded replacement part and it worked just fine on an M50? I'm wondering if it was compressed like mentioned above or if when oil pressure is applied, it will pop out to normal length/operation like the E39 tensioners.



Thanks!

UPDATE: Figured it out. It works. Once compressed, they do the same job and the new one is way easier to install than the E30, E28 or E39 tensioners.

[bluemax]

i had alot of engine knock noise, so i drained the oil and found small metal pieces that look like piston ring parts. i have a 97 m3 six. are there piston sleeves installed on the block. i know i have to overhaul the engine.