I am concerned about my timing chain. My records show that it is original (340,000). My manuals/CD do not show how to check for stretch, or I just can't find it. I intend to replace the chain itself, next spring when it is warmer. If my chain is loose will it be obvious aurally, and especially with a stethoscope? Does anyone use offset keys to correct the stretch anymore? I see that to change it, I attach the new one to the old one and rotate the chain around very carefully. I will replace the chain tensioner, should I also replace all the rails? Let's talk timing chains!!!!

I too would like to hear some input from the expert's on this topic. I'm getting a little gun shy on my 83 300D 186K. I may be premature in worrying, but failure of this componet can be very costly. Probably more than the car is worth. An ounce of prevention.

[Edited by shoe on 12-28-2000 at 09:17 AM]

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Keith Schuster
2006 E350 98K miles
2013 Ford Explorer 15K miles

The timing chain stretch can be checked using a dial indicator on one of the valves in the number one cylinder. You will have to get exact procedure from a factory manual. It is not difficult if you have the procedure and the dial indicator.

Timing chain stretch rate is closely related to oil change frequency. If the oil has not been thoroughly and religiously changed, the particulate matter in the dirty oil will wear the chain rapidly.

I have never had a chain failure in a 616 or 617 motor, but I do know that, if oil changes are neglected they can fail.

The chain is so easy to replace, if you're worried, roll a new one in. It's probably the second cheapest engine insurance you can buy behind frequent oil changes.

Good luck,

Thanks Larry,
I have all the factory manuals, and I have seen that procedure. I guess I need to keep looking. Do I need to replace the three different rails when I replace the chain? I would be less reluctant to change the chain and most likely the tensioner at the same time if I could leave the rails alone? Are my rails likely to be worn if they have 340,000 miles on them? Thanks for the response. I was wondering where you were. Welcome back!

I would expect the rails to be worn. Unless there is a problem with the tensioner, I wouldn't bother replacing it. The rails would be more important to replace. But the most important thing would be to simply roll in a new chain.

Good luck,

If the engine pointer hasn't been moved a dozen times to do front crank seals, then with v/cover removed; align cam marks & look at the crankshaft. If the crank is more than 3deg off then it's time for new chain!!! While you are there, check the valve adjustment too.

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Thanks! I think that will work for me. I did a valve adjustment this past summer, but did not check the chain at that time.

Patsy, If you have the MB service manuals, check the one for "Engines 615,616,617.91"page 05.4-215/5. there it tells about replacing timing chains.If you do replace the chain, how about the cam sprocket gear? It probably gets more wear than the chain. Make sure the tensioner is good. It's there to keep the chain good and tight. When I do replace a chain, I will always replace the cam sprocket and the tensioner if needed. Good Luck
Bill Lewallen Lexington,Ky.
If I listed all the Mercedes I have owned, It would take up to much space. Let's just say I have owned a few.