On my 99 E300 (200k miles) the pulley came off completely a few months ago and damaged the alternator shaft and broke a couple of fan blades, requiring a new alternator and fan. The cause appeared to be that the bearings in the pulley froze up. From the way things must have been thrashing around down there, I think I'm lucky the radiator wasn't damaged. The pulley contains a clutch of some kind and roller bearings. My mechanic, who has 30 years of experience at a Mercedes dealership, has seen it before, and says he used to tighten this pulley on every one of these cars that came into the shop. Steve

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1980 300 TD

1997 Dodge Pickup/Cummins 5.9 12-valve