I've had my XC90 for a few months now. Heard a high-pitch squeal from the engine compartment and assumed it was a belt so just waited on it. That was a couple months ago. Then the other day it seemed to get worse, quickly. Then the squealing stopped and all my power (steering, coolant, etc..) went out. The serpentine belt had come off. Mechanic initially said a pulley had come loose or something and it wasn't a big deal. Later, when he actually went to replace the pulley, the idler pulley came off and the bolt that it was connected to was mangled. It hadn't sheared completely off, but did not look good. That's going to cost me $1200-1500. Not happy. Anyone know what could cause this or has heard of it happening?