Anyone with access to the EPC, would you mind giving me the part number for this? It's number 75 below.



All I can find is 1109933901, which is not the right spring.
Apparently it's different for om615/16's and for NA om617s up to 81.

Seems like a good idea to replace.

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1981 240D 4sp manual. Ivory White.

Alright, the number is 6219930201

I certainly will not be the last person to ask for it.

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1981 240D 4sp manual. Ivory White.

Well this has gotten exciting. I can't find a mention of 616 tensioner maintenance in the archives so might as well track the misadventure here.

Got the spring and the crush washer at the dealer -bought $3, no problem.

Started by removing the 22mm cap. A little oil dribbled out and this is what I found:



I was expecting the spring to push the innards out against the cap, at which point I could collect them, and then reassemble using the new spring.

Now I'm not so sure. In fact, I don't know if I can just put the cap back on. I'm reading about priming these things, and filling them with oil, and so on so forth and my concern now is that I've somehow lost pressure in the tensioner or simply drained its oil.

I'm not sure what to do... I'm hoping one of you has been there before and can advise me.


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1981 240D 4sp manual. Ivory White.

No takers?

I’m very curious about what’s holding that end cap in place.
If you look at the diagram, it doesn’t appear to be tapered or threaded... and yet, it’s standing up to the force of the spring.

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1981 240D 4sp manual. Ivory White.

Sludge in bore trapping the piston and/or spring completely collapsed?

Try to move the piston in a bit to break any adhesion.
If it moves in but doesn't return to the start position, use a magnet retrieval tool to
remove the piston.

Edit: After closer inspection of the diagram...
There is a clip (item 71) that probably attaches to the rod (item 76) holds the assembly together.
You probably have to remove the whole tensioner to disassemble it, and replace the gasket (item 85) as well.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Now we’re talking. I’m considering removing the valve cover and checking the chain. Could always press a little against the tensioner from that side, I suppose?

Edit: just saw your edit. Excellent catch... I mistook that for an O-ring.

I think I’ll put the cap back on with a fresh washer and save the rebuild for another day.

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1981 240D 4sp manual. Ivory White.

No problem reinstalling the cap with a fresh washer and driving away.
Checked the chain anyway, and everything was fine.

Since there is hardly any info on this, I'm putting it here for future reference.

The tensioner on NA 617 and 616 engines is quite different from their Turbo counterparts.
Say for installing a woodruff key or rolling a new chain or whatever, you cannot simply remove the spring to relieve chain tension.
You must remove the tensioner. This means a new gasket. This also means draining the radiator and disconnecting the thermostat housing (which requires another new gasket).

It's possible to rebuild the tensioner, but I believe there are some internal seals in the piston that are not serviceable (I'm not 100% on this).
From what I can tell, there are two channels carrying oil in and out of the piston. I believe this provides additional tension as oil pressure increases.
The spring seems to be responsible for tension only on start up, as oil pressure rises, and probably in the instance of oil pressure loss.
There's a lot more going on in this model than the others. So while you can still find many of the parts, I'm not sure it's worth the time.

I am curious though if 617 turbo tensioners are backward compatible. Does the chain on a 617 turbo require a different tension?
If not, this seems like a good move.

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1981 240D 4sp manual. Ivory White.