Timing chain tensioner wear after 30k miles

[JHZR2]

Hello again,

I also replaced my timing chain tensioner today.  40k is a typical replacement regimen, I guess (none is given by OE) but I did mine a bit early since I was doing a bumch of other stuff - this one is 30k old.

Here they are:

 One was extended, one wasnt.  Both are the "Updated" M44 version (the original BMW M42 engine version was slightly different in terms of oil passageway).  

Here both are lined up, both are extended, and I lined them up as closely as possible:




Its tough to see, especially because I wasnt shooting with a tripod, so couldnt be really exact... but the old one does show some wear.  

There is also some wear around the piston:





They do wear, and so folks may want to consider replacing them... they seem to wear faster than one would think!!!

JMH

[sheepdog]

If you are going through them fast, and it looks like you may be, you should probably pull the cam cover and take a look at the sprockets.

[D. Clay]

So tension increases with oil pressure/RPM and chain pressure on the guide rails also goes up. I had never really thought about the tensioner piston moving in the outer sleeve until now. Duh! Obviously that is where the wear comes from. The type of driving would come into play. The more frequently the RPM changes and the amount of change would make the tensioner wear faster. The problem is more pronounced on the M42 due to keeping the RPM up but that's part of the fun of driving one.

[sheepdog]

So tension increases with oil pressure/RPM and chain pressure on the guide rails also goes up. I had never really thought about the tensioner piston moving in the outer sleeve until now. Duh! Obviously that is where the wear comes from. The type of driving would come into play. The more frequently the RPM changes and the amount of change would make the tensioner wear faster. The problem is more pronounced on the M42 due to keeping the RPM up but that's part of the fun of driving one.

Excessive movement can be a sign of chain/sprocket wear.

[JHZR2]

but how do you really characterize excessive movement???

Most chains are good for >>100k, even in diesels. I know we've seen that the M42 chain is apparently not as good for whatever reason, but there ought to be some sort of a real metric.  

For example, in MB diesels, they sell offset keys for up to 8 degrees of "stretch", which means that the chain can be worn pretty far and still used, and offset to the correct timing.  If our chains/sprockets are of an inferior metal, ten so be it, but it seems tobe that there should be some real metric behind it...

Is there a DIY on removing the cam cover??? How involved is the job,especially if I decide to replace the chain and ALL sprockets, guides, etc.?

Thanks,

JMH

[sheepdog]

Pulling the cover is easy, pull the plug wires, pull the bolts and lift.
Pretty straightforward, 5 minute job.

I am sure there is a maximum stretch, all chains have one. What is that number though? I doubt anyone knows. Best way to tell is to watch the cam sprockets, if they show any wear, you know the chain has stretched too far. Still safe, but it will only get worse at an increased rate from this point.

Pre-emptive replacement is hard to judge. However if you ask me, it is pointless. The amount of work, and time to just replace the chain is not worth the effort, just let it go till the whole assembly needs replacing. Besides, you can replace just the chain, and it will stretch to match the sprockets that had already been worn by the last chain. Always best to do it as a unit. Considering the cost, it is better to get as much life out of it as you can.

[JHZR2]

OK, so it is just under the valve cover... I was under the impression that you meant another cover.  

MB offers offset keys up to certain sizes.  Id have guessed that BMW would have simlar things... and one can assume at least that if you have more stretch than you can get an offset for, then your chain needs replacement.  

IMO, the BMW is inferior if it is proving to be work at 100-200k.  My MB diesel has less than 1 degree at well over 200k.  Justmeans more work, but perhaps even in this forum we can devellop some insight and good guidelines.

JMH