high rpm serpentine squeal

[happier days]

Sounded like an easy fix to me too. 2005 Pontiac Montana 3.5l. Power steering pump was leaking, just took to shop to replace. They said the tensioner was bad and needed to be replaced. Ok, thats easy.... the previous owner(s) broke the top off the bolt so now its flush, im also convinced that they mounted it wrong. 90 inch belt not able to turn the alternator enough to charge. Charging system failure displayed after driving. Replaced with a 88 1/2 inch belt that can turn the alternator. Not a fix but simi-drivable. Belt slippage under acceleration along with loud squealing. A smaller belt would rub against the tensioner (parallel to ground rather then perpendicular like in the diagram). Any ideas?

 

[Steelcity]

If it were me I would start with a new tenioner arm and pulley and I guess a new bolt(s), then a stock belt ,then everything should be fine if not then look into each rotating device ie: ac or water pump or alt for the squeal. But I think once you get back to a proper working tenioner and correct belt you will be fixed.