The noise is clear during idle and it's coming from front of the engine. But it goes away when I push on the accelerator. My friends insist that it has to be a bearing or something similar in one of those pulleys.

But I thought if it was a bearing, then it should be making noises at any rpm, not just during idling.

I have searched the forum and some mentioned the similar symptoms with a fix of changing motor/trans mount. Can the engine mounts failure cause these nailing/vibrating noise @ idle, and quit at acceleration?

The Benz is the 96 E 300 D.

What failures will cause engine nailing noises during idle but quit at higher rpms?