I think the dealer is just trying to take your money.
Based on all the experience of the techs that post on this site, none of them ever recommends timing chain replacement on a six-cylinder engine like yours. The reason is that the chains do no stretch or become loose. The chains are very short, and don't change direction (like the chain on a V8 engine).
Further, these M103 and M104 (yours is an M104) engines have a ratcheting tensioner, which is another reason for timing chain durability. It uses oil pressure as do others, but as the chain loosens the plunger "ratchets" to keep the chain tight, even after the engine is shut down. Since there is no looseness during that cold start up, it does not hang up on "stuff" causing things to break, like timing chain guide rails.
The V8's use plast guide rails (which break as they become old), but I believe your engine uses metal guide rails.
Anyways, the dealership replaced your tensioner, and this should be keeping your chain tight.
If you still hear a noise, your chain is not the problem.
I would not take your car back to the dealer, but rather take it to an independent garage that specializes in Mercedes Benz vehicles.
My $ .02,
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
Last edited by suginami; 10-20-2002 at 09:36 PM.