The other day I noticed that my alternator belt was a little loose. I was going to get to it this weekend, but I started to hear some squealing that I thought might be the belt. I tightened the belt and expected the noise to be gone. To my surprise it wasn't. It's a squeal/screech that seems to be coming from the rear of the engine itself. When driving it would stop if I accelerated, then come back at idle or while coasting. It's loud enough to make me not want to listen to it too long while troubleshooting. I looked around, but couldn't see what could be causing it. Any ideas?

Thanks for your help!

Eric