Well about a week ago I bought a new belt for my truck, it ran quiet all until this morning, turned truck on, and it squeaked, quite louder than before. I'm thinking it might be the pulleys, but I'm not to sure.

 

it must be is your tentioner pully ceazed if not check your ac pulley mine squeak a little bit to but my ac pulley is warped so it hittin on the pump a little bit

 

use WD40 , spray at the pulley , its either dry and got moisture at the nut and pulley , or the pulley is shot , but doing this you will find which pulley it is...

 

I'm gonna try the WD-40 trick on mine. My belt is in great shape but I have a squeak when it's cold. I'm thinking it's the tensioner pulley or the pulley on that front bracket.

 

My step dad told me not to spray WD-40, I'm not to sure why, would I spray lift the belt up and spray the wd-40 underneath the belt and all around the pulley?

 

don't use WD 40 on your belt - it'll dry it out (the WD stands for water displacement, check out their website).

 

Pop the belt off then spin each pulley and listen for clacking in the bearings.
Check for wobble or stiffness in the pulleys.
Check out the idler pulley and the water pump pulley for a glazed layer of gunk on them, if it's there then hit it with some 400 grit sand paper or a razor blade to get that gunk off.
Check the ribs on the other pulleys for any contaminants in them.
Put the socket on your tensioner and move it in as far as you need to for belt installation and make sure it doesn't bind up at all. My original belt tensioner would stick really bad, I had to grab it and pull it toward the passenger fender when I put the belt on just so it would put some tension on it.