The tensioner nut came off my idler pulley, releasing the pulley and letting the belt come off as I was driving. I believe the bearing seized and spun the bolt, and that's what caused it. The new pulley I got from auto one is a 25mm,but the bearing is shorter, and the nut is contacting the bolt shank without securing the pulley. Should I replace the bearing on the old pulley, or should I just keep hunting for a new one?

Where did you purchase the pulley? If it's not the correct part, return it to the place and keep searching. Also, how hard does the bearing look to get out of your old part? Maybe you can use the bearing from the new part and press/install it into the new part.

I've never had mine off so I'm giving advice blind here. But I think that if the new part didn't work, I'd ask for my money back and buy the correct part.

Just out of curiosity, how loud was it before it spun off? Seems to me the bearing would have been letting you know it needed replaced before it locked up.

Tom

The bearing seized, and was ground flush with the pulley. It was useless. As for the sound, it wasn't making any. I had a whirring sound, but I attributed it to a replaced power steering pump that hadn't finished bleeding yet.