Hi,
I have ML 350 -2003. lately I hear like "uncreased pully" noise ONLY while driving, nothing when parked and engine running.
The noise is more obvious when going down the hill.
Sometime it goes when I step on the Gas; sometime is starts when I step on the Gas.
any help please.

TonyBH

 

I would love to hear a sound clip. You need to try and locate the area it is comming from. Engine/drivetrain. If it is a roaring type noise it could be tires. Check the tires and see if they are chopped on the inner or outter edge.

 

if its while driving could be the center support bearing of the drive shaft. they do go bad and youll hear it under the second row of seats. it will get louder with time. or maybe front diff noise they go bad too. diff makes a kind of grinding sound and support bearing makes a whine sound.