1999 pontiac grand prix gt squealing very loud when it hits operating temp

https://www.bing.com/search?q=2004+grand+prix+serpentine+belt+diagram&form=EDGNTC&qs=AS&cvid=738d3f0931444115b44f6f066f182f85&pq=2004%20grand%20prix%20ser

If the belt is squealing, I would take it back to the mechanic.
Could be a pulley not aligned with the others, or a bearing problem, or the belt is not installed correctly.

its suppose to move up to 1/2", it is spring loaded!! Now if its squealing or chirping at startup or when the engine is revved, the tensioner is probably worn and needs replacing along with the belt!!

It sounds like a belt thats slipping. You have a sticking puley somewhere, take off the belt and rotate all of the pulleys. Usually its an AC compressor pulley so pay special attention to it. The whining noise that it makes while turning, is it the same as the squealing noise? If so it could be a problem with the pump, check the fluid level and see if its an odd color or has an odd odor (like burnt or black). Hope this helps!

THE FRONT BEARING IN THE SUPERCAHRGER HAS GONE BAD. DO NOT DRIVE IT TIL' IT IS FIXED.
YOU WILL GET STRANDED AND MAYBE RUIN THE ENGINE IF PARTS GET SUCKED IN THE INTAKE.
ROBERT

The are only suposed to come on when the engine temp starts going over operating temp, like standing traffic. if then they don't work check the engine temp sensor

SOUND LIKE BLOWER MOTOR SHAFT BEARING FAILING CAUSING SQUEAK NOISE.

I would start with a belt. While removing it feel how much tension the tensioner has on it, on the 3800 egnine they have a stiff tensioner(sorry I don't have any specs for how much) After you get the belt off you can look at all of the pulleys and spin them to see if the bind or look for stuff stuck in the grooves on the pulleys.
It sounds to me like the belt is streched. I would not recommend one of those gator back belts, they seem to make more noise sooner than a good v notch belt. But thats just my opinion!

check your belt tension. Tighten it up and the noise should go away. if not, replace the belt and tension it accordingly.

Sounds like u have a pinched line somewhere?? have you checked yours lines??? if u have and no pinch sounds like ur power steering went bad and it's not hard to change...