C200 Front end engine noise at idle only

C 200 Auto has a noisy front end at idle in vicinity of water pump and belt tensioner pulley. When any revs applied in neutral or drive, noise disappears. Suspect water pump?

Also, the vehicle has another rattle, a much lighter noise at 1500 rpm in all gears, but not in neutral. Above or below 1500 rpm, no noise!No issues with transmission gear shifting. Sounds like an exhaust shield/bracket or similar? Or could it be the Cat?

KJQ

Most likely the belt tensioner shock but I wouldn't rule out the tensioner either. When the engine is running push a screwdriver blade against the shock end and see if the sound dissapears.

Most likely the belt tensioner shock but I wouldn't rule out the tensioner either. When the engine is running push a screwdriver blade against the shock end and see if the sound dissapears.

Thanks for your help. Your diagnosis was spot on. Replaced the tensioner damper and all is quiet.:)