M115 timing chain tensioner

[Mike D]

115 050 11 11

Are the M115 timing chain tensioners rebuild-able? I imagine they are but I don't want to tear this one apart and find out they aren't.

The engine has a slight "slapping" noise when first accelerating from a "hot" idle (oil pressure at its lowest point, apx. 25PSI) which ceases when the RPM's increase and the pressure rises.

The tensioner also fully collapses when the engine is shut off. I know this is not correct for any every other Mercedes I have seen but don't know if it is normal for the M115.

[Diseasel300]

Looking up an image of your tensioner, it looks like it should come apart for cleaning. I redid the tensioner in my OM603 for the same reasons as you. Varnish was the enemy, everything was clogged up with it. Since cleaning, it's been fine.

WARNING: Make extra special attention to the FSM on the installation procedure for your specific engine! Some tensioners have a specific installation method and can ruin the chain or camshaft if installed incorrectly!

[Frank Reiner]

Mike,
The tensioners of the M115, M130, and OM615/616 appear (from parts diagrams) to all be the same internally. The M115 and OM615/616 tensioner bodies also appear to be the same, while the M130 has a different body. The M110, however, is different internally; there is a ratchet mechanism which is not found in the earlier style.
So, to answer your question, it would seem that your tensioner is readily re-buildable, with a particular eye to spring condition. That it goes slack without oil pressure suggests that the spring is in trouble.

[Mike D]

Thank you gentlemen.

I was a bit leery of tearing into the part, especially since the replacement costs I found were in the $280.00-ish range. I've since located a supplier which lists the part at $70.00 so I feel a little more comfortable.

I don't mind trying a $70 experiment.