Car: 1993 500SEL

A grinding noise is coming from the front of the engine - "by the belt".

As best as I can determine - it's coming from a device on the belt, on top of the alternator. The black plastic on the left of it vibrates simular to the grinding noise.

Is this an air pump?

Thanks for your continued help.

Comment: I just had the water pump replaced - what is it now?

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Thanks for the help
Bill Fisher

'86 560SL (186K) - Now a 'classic' : Registered as an Historic Vehicle
02 E430 in the stable
'14 LS460 (Lexus)
- - - - -
'95 E420 (198K) found a new home
'99 E320 (80K) (gave it's life for me as we hit a bumper)
'95 E420 (231K) Sold to a happy buyer, new to Mercedes
'90 300E (65K) Sold to an Mercedes Lover
'92 190E (215K) - retired to the salvage yard
'93 500SEL (214K) - Moved to another family, still runs like a young pup