athenshome

I was just driving my wife's 1999 ML430 and notices a strange humming noise coming from the engine. It sounds like it is coming from the fan and/or belt area, but it is not a squeal or chirping sound (more like a humming). It only happens when you're accelerating, not idling.

Any ideas on what this could be or where to start looking???

Maj. Dundee

Remove the belt as per instructions and then by hand spin 4, 6 & 7 probable and 2, 3 & 5 possible.

athenshome

Will do. Should I be looking for anything in particular when spinning these wheels or just to confirm they do spin?

Maj. Dundee

Come on, noise of course and difficulty turning.