The dreaded chirp from the serpentine belt....fixed
 

Went through this motor 18 months ago, everything new on the front of the motor. Chirping when accelerating, quiet when the RPMs drop. Did the usual, new AC and serpentine belt, tensioner and idler. Alternator was original so put a new AC Delco alternator on.

It was quiet for 2 or 3 days and then started up again. Drew a white line on the harmonic balancer and took it for a spirited drive. So much for a TRW harmonic balancer.... The outer part of it shifted about a quarter inch on a 20 minute drive. Also it was about 2 mm out of line with the power steering pulley. Bought a new genuine GM harmonic balancer, replace the front timing cover crankshaft seal just because.... Inspected the water pump pulley. Spin it normally by hand and it's quiet. Typical resistance. Spin it fast by hand and there's the squeak. Rocked the pulley and what do you know, about a millimeter of slop in the water pump bearing. (US Motor Works pump....never again)

https://cimg2.ibsrv.net/gimg/www.hum...cef041ded1.jpg

Glad you got it fixed, the parts today are such garbage, guess they think everyone wants the cheapest POS to get them by, I will gladly pay a premium for good stuff.

Had that same squeak after I had a local garage replace the front crank seal (leaking) and they would only do if they installed a new harmonic balancer also... so I get back with a squeak and a leaky "new" crankshaft seal. I just took it to a local GM dealership and they ended up re-doing the crank seal - has been leak & squeak free..... Was last time at the "local garage" for me, figured if they screwed it up from the start- they were not touching it a second time, regardless if it was warranty work. Squeaking belt is annoying as hell, was so glad GM service center resolved it.

The other thing I did was to get rid of the AC belt tensioner, I went with a stretch belt like the newer models.

If you have the style with the AC belt tensioner, you can ditch that and use the AC Delco 4K355SF. Goes on the same way you would on a newer model Escalade or a Tahoe.... Put the belt all the way over the crankshaft pulley and behind it, still a belt over AC compressor, bring the belt to the top of the crankshaft pulley from behind, well a zip tie through the crankshaft pulley and up over the belt tight.... 24 mm socket, rotate the crankshaft clockwise until the belt is all the way on. You'll never have to mess with that AC belt tensioner that never lasts too long.

Interesting, that is a great tip.

I think GM gave up on those little AC belt tensioners because of so many failures. It's a really small bearing in it.