A couple of years ago my tensioner went bad and I rebuilt it using a combination of stuff including some L98 parts and an aftermarket aluminum pulley from UPR products (the pulley specs as a 85-93 Mustang ultra light tension/idler pulley). I followed the tensioner rebuild project of the Forum, so if you have this pulley I suggest you check it.
I can't think of any reason other than poor build quality as the cause, there are actually several holes although you can only see the one in the pic. The belt shows some damage too, I was noticing some odd coolant temp and voltage fluctuations which is why I started poking around. Guess I'll go back to the factory pulley.
