For the past two weeks or so, my truck (2005 F250 6.0 Auto, 4x4, CC, SB) has been making a high pitched squealing noise at idle RPMs. Anything around 800 RPM it will squeal. If I push the accelerator a little, say to 1000 RPM it goes away. It mostly will squeal when the truck is cold, but it has done it when warm as well. It will make the squealing noise stopped and when driving.

I had the serpentine belt replaced approximately 5K miles ago.

I tried figuring out where the noise was coming from on the engine, but had difficulty pinpointing where the noise was coming from.

I'm taking the truck into the shop for an oil change next week. Any ideas where I should have them start looking for this squeal?

 

Take a spray bottle with water in it and spray the belt while the truck is running. It will at least eliminate the belt and pullies or give you a place to start.

 

It will probably be the belt tensioner pulley or ideler pulley, mine had the squeal, changed my belt helped for a month, changed out my belt tensioner assembly and it has helped so far no squeal when cold.