Squealing engine noise

The other day I started my truck and had some squealing noise. In the past Occasionally when it’s moist I’ll get a few seconds of squeal when first starting the engine, how this is of a different pitch. I have a manual transmission and seemingly the noise will dissipate in between gears but return as I release the clutch. The level of squealing however is unaffected by an increase in speed. I opened the hood this morning and started the engine in neutral. The noise builds and fades and builds and fades. Seemingly two different pitches. I’m assuming this has something to do with belts or pullys or wheels....just wondering where is a good place to start trouble shooting? Any advice is greatly appreciated!

 

Throwout bearing in a manual transmission will squeal like this. If its happening on startup it might be one of the drive belts, I would start by checking the tension on all the drive belts as it's cheaper and easier than replacing a T/O bearing.

 

take the accessory drive belts off and start her cold, if it disappears it is one of them, if not and it persists then is it coming from the front or back of the motor. From the back as suggested above, T/O bearing front probably a timing belt idler/tensioner.

 

Perhaps your belts are old? Perhaps they need tightening? Perhaps your belt bearings or pulleys need changing?

I had a similar problem to yours, where the noise would fade and such, a short while ago. It turned out to be the A/C idler pulley. The noise would increase as I pressed the gas. It was a sort of rumble/howl noise, and not as squeal-ly. It made me think it was something to do with the engine, but I had to pin point it by leaving it on, opening up the hood, pulling on the throttle cable, and getting an idea of where it came from by listening closely.

Here's a good video on this sort of problem by the way.