Afraid of the answer.....

[Qmulus]

Originally Posted by robdelorenzo

Yes, the pulley sheared off (as seen in the photo) it's gone and nowhere to be found.
The belt was from Pelican and I'm pretty sure it was the right one.
The alternator still spins, the water pump spins, the rollers still have the required "resistance" (they don't spin for very long) The belt didn't even break!

I'm holding good thoughts that an alternator, a belt, a fixed hose and away I go!

It is just semantics, but the alternator clutch/pulley did not shear off, it spun off. If it had sheared the shaft, you would have a snapped off alternator shaft. It looks to me like you could just install a new clutch/pulley assembly and it would be OK. The alternator has a one-way clutch on it so it will continue to spin and not throw the belt when you shift. This is kind of unique and not usually seen on other cars. What may have happened is that the clutch seized (they do fail occasionally) and when you shifted the momentum of the alternator unscrewed the pulley from the shaft and the pulley fell away. Normally the one-way clutch would slip in that situation, as it was designed to do. After that, the temperature and pressure in the cooling system got so high that the weakest point failed (that plastic fitting) and the cooling system blew. I don't understand why the cap wouldn't vent though...

That is my theory anyway. I bet if you look where this happened you will find the pulley pretty much intact on the street.