triggerman

I know I will sound like a little old lady trying to explain a car noise to her mechanic, but oh well. When the engine is running (95 M104) sometimes it makes a slight bump, bump sound that follows along w/ engine rpms. Sometimes it goes away, at first I thought it happened when it was cold, but upon further monitoring, that has nothing to do w/ it. Then it seemed to go away when the compressor was off and begin when it came back on, but I had the wife hit the "economy" button on CC while the bump, bump was going on, but it continued. Anyone else experienced this. I have stuck my head all over the eng compartment while bump was going on and cant locate the source. The fan is not hitting the shroud or anything else it seems, and the aux. fans are off at the time. Any ideas.

Thanks
Triggerman

NorCal124

Engine mount

triggerman

Thats an idea, however, the engine does not torque badly when started and no fluid is leaking or can be seen around the mounts.

I have been listening to the engine more and now the "bump bump" does seem to relate to the compressor comming on. Goes away when compressor goes off to a great degree. Dont know .

Triggerman

Z300E

I heard a similar sound and it turned out to be the Accessory Belt Tension Damper. It's a small shock that cost me around $40.00 from the Benz Bin.
Might be worth taking a look at and it is an inexpensive part to change out.