Noise and the pulley moving in an untrue fashon are signs of bearing failure. If this happens, replace soon.
If you do-it-yourself, we could get you one through the partsshop.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM