When my truck is idling in park or drive there’s a high pitched squeak coming from what sounds like the engine bay. I’m positive it’s not the belt, I replaced it a few months back. The noise is off and on its not constant so I was thinking it was the idler pulley but not sure. Don’t want to blindly replace parts and spend unnecessary money thanks

 

The idler pulley will often do that when it gets age on it. Just about any engine with a serpentine belt can do it. It will usually be worse when it's cold. Spray a little oil onto the pulley from behind onto the bearing. /if the squeek stops, you've found the naughty one.

 

Can also use an extension or similar rod to listen to each pulley as it runs. Just keep you hair from falling in the belt!

 

A little bit of dirt on one of the pulleys will also give you a squeak, or a weak belt tensioner.

 

Well my truck has done this every time i have replaced the belt. The pulleys wear (get shiny) and when you put a new belt on it can cause it to squeak until the belt wears in then it will stop. This is if all the other factors check out to be good.

 

This right here I went through 5 belts when I was younger until my dad told me that