T.chain purchase?
 

Hello, I am working on a 1978 300cd no t. My vehicle runs good all around accept at idle. I have checked the timing chain and it appears to have a considerable amount of stretch. I plan to rollin another timing chain. My questions are what do the Brothers of the Benz recomend me purchasing other than the chain? What other replacments are recomended while I am doing this? E.G. chain rails? tensioner? guides? The second question is. What would be recomended after the chain install? valve adjustment? fuel injection pump timing? thanks for any help, great website!
CD in S.C.

headstill,

someone else must also answer with specifics but my mechanic does think you need to replace one or all of those ancillary items you asked about when doing new chain. Sorry I can't remember which one(s). I do remember that the added parts were pretty expensive, unfortunately.

Nic
'85 300CD

Replace the tensioner too. Take a look at the slide rails and if they are worn then you will want to change them too. A little more complicated than just the chain and tensioner. The wear on the rail will be based on the frequency of oil changes.

Heasdtill,

Chain replacement will not affect valve adjustment but it might be time for it anyway. It will affect the injection timing so you might check that and adjust if necessary. If the chain tensioner works OK I can't see replacing it. If the chain guides and rails are worn, replace them too. They aren't that expensive.

How much is your valve timing off? Up to 3 degrees on crankshaft pulley is OK. You might also consider installing an offset woodruf key to correct the valve timing. That way you don't have to replace the chain. This part is available from fastlane.

P E H

How can one tell if the chain tensioner is working ? Does that just mean that the chain has not jumped a sprocket ? I would take the safe route and replace it also while all those things were already off where you can reach it... Greg

At least disassemble the tensioner and inspect the spring. On my 300D when I replaced the chain I found that the spring was worn approximately 1/2 way through where it had been rubbing on the side of the housing since 1985.

Leathremang,

You can tell if the tensioner is working by feeling if the timing chain is tight. If there is any slop in the chain when pushing it back and forth with your fingers, something is wrong with the tensioner.

It could be a broken spring or just jammed like one I had.

P E H