Originally posted by Doug McCutchan
...This might be peculiar to a M102 230 motor in a W124 chassis.
Nope. My 1998 C230 (M111.974) W202 chassis has the little shock, and it has indeed worn out on my car. When the eninge is cold, and the shock is cold, it can make a rattly noise. Also, the tensioner itself can make some knocking noises, though mine just let the belt squeal a bit when going bad.