My '89 560SEC runs well, and I am a happy camper every time I slide behind the wheel.
Having 129,000 on it, and reading up on the subject, I have to ask about the timing chain, guide and tensioner.
Depending on who you ask, the guides are:
a) composite, and last a long time with no trouble; or
b) plastic, and become brittle with time and can cause the engine to self-destruct.
I had the passenger side valve cover off, and everything looked good. The two guides that are visible appeared to be a darkened with age, but otherwise appeared intact.
Also depending on who you ask, the chain is:
a) good for another 20,000 miles; or
b) overdue for replacement.
Again, the duplex chain looked good.
Is there any objective way to resolve these issues? What is the official MB position? Is that realistic?