My '79 300D clatters and clanks pretty loudly in the a.m. when it is cold. It stays that way until it hits operating temp.at about 100-150 degrees. I don't hear it any more, even after sitting for a few hours as long as it's sufficiently warm. Someone mentioned the timing chain, but the tech who did my minor "tune-up" told me not to worry about the T-chain until I hit 100,000...I'm at 90,000 now. (He didn't hear the clank as the car was warm). Should I be concerned?
Thanks,
Joe

My '77 300D made lots of noise (knocking/nailing) until it was warmed up also. I guess that's part of the charm of owning a diesel, the sound of pennies in your piggy-bank, as they say. I've heard that could be weak glow plugs, but I used Red Line Diesel Fuel catalyst in that car, and it claimed to reduce "nailing." It's pretty cheap ($4.59 at Pep Boys, I think). It didn't do any harm, and a couple times it seemed like the car had real power(!)

The local independent garage in Allentown PA recommended 150K miles as an interval for changing the timing chain, 100K for gas engines. Not sure what MB recommends.

Umm...I hope you mean 100-150 degrees fahrenheit(sorry about sp)? My 300D runs about 80 centigrade...
Jon