Dandy. I guess I could see the cover rubbing on the belt if it was mispositioned but it should have made noise and been noticed right away. I don't think that would cause a pulley problem though. That's asking plastic to cut steel. I don't know which engine you have. Some of them do not use a spring-loaded tensioner pulley for the generator belt. Those belts have to be manually tightened. I wonder if the previous mechanic over-tightened it after replacing the timing belt. That could stress the shaft on the generator and possibly lead to metal fatigue. Even that would be quite uncommon. In severe cases it's the bearings that would be damaged first from the excessive belt tension.
There could also be a totally different cause of repeat belt failure. That is one the components it drives is locking up intermittently. Normally you would suddenly hear a loud squeal unless it happens so quickly that the belt breaks right away. Generators have been known to lock up when a bearing fails. That's actually pretty common on GM vehicles '87 and newer.
If something else is causing the belt to stop abruptly, that could cause the generator pulley to stop spinning, and the momentum of the rotor might cause that nut to work loose so the pulley could fall off. I'm really tired now and not thinking clearly. Instead of thinking of every remote possibility, I'll check back tomorrow to see if you've made any progress.
Thursday, October 10th, 2013 AT 4:23 AM