I have a question about alternator repair.  A noise, like a vibration, started suddenly while driving.  On inspection I found that about 1/3 of the alternator fan had broken off and embedded itself in the engine cover (also making about a 1/2" hole in the cover).  My question is what might be the underlying cause, perhaps the end bearing?  Or just a metal failure?  The alternator, which is Bosch and about 8 years old, seems to be charging fine but the vibration noise is still there.  Just replace the whole thing?

Dave B.

Boise, ID