I've got an '83 240D with 243,000 miles that has some pretty bad timing chain slap. I'm planning on replacing the tensioner soon. Does anyone have any advice on this job? Yes, I have the service manual. It looks pretty easy.

How do I know if I need to replace the tensioner rail as well? My mechanic mentioned that the plastic rail might be in bad shape due to the chain slap, especially since I've had that problem for a while. I really don't
want to have to replace the tensioner rail, since it looks like a helluva job.. according to the service manual "Step 1: remove radiator and fan." Ack. But if it needs replacing, so be it. How do I tell?

Also, should I consider replacing the timing chain? How do I know if it needs replacing? From what I've heard, timing chains generally don't need replacing, but if I've had pretty bad chain slap for a long time then mine
might be damaged. How can I tell? I certainly don't want to leave it alone, then later find out (the hard way!) that I should have replaced it.

Thanks in advance.

- Nathan
'83 240D, 243,000 miles

Take off the valve cover and roll the engine with a wrench to Top Dead Center (TDC). Then you should see a mark on the thrust washer of the cam. The mark should be starting to line up with the line on the cam tower. Roll the engine in a clockwise rotation untill the lines are perfectly in line. Read the degrees on the crank. More than 4 or 5 and you have too much chain stretch. If you are doing this type of work, plan on the rails and tensioning rail too.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SHOP MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

With 243K on the timing chain it would be in your best interest to go ahead and replace it along with the tensioner. As for the chain guide, do it. I just recently had a 420 SEL that someone replaced a chain and tensioner within 4K miles and the guide broke and as a result the engine had 6 bent valves. Believe me, if the guide breaks on a diesel you'll have more damage than that to deal with.

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ASE Master Technician, Lead Technician-Deutsch American Inc. Over 6 years of Import Service-specializing in German Automobiles.