I was driving along and the alternator clutch pulley seems to have sheared in half, snapped the belt and the engine is sprayed with fine irom filings. The only warning was a light buzzing or vibrating noise for a few minutes before. Then the stop and battery light came on.

So, the pulley is still attached to the alternator but tabout half of the ringed or ridged section has gone. What would cause this, is it a common fault and does it mean my alternator needs replacing?

Secondly, Does anyone know the proceedure for replacing the alternator/pulley and belt? It looks very tight in there.

Any help appreciated. Thanks