2001 Ford Mustang V8 Two Wheel Drive Automatic 107500 miles
Engine accessory belt squeals upon starting, have replaced idler pulley. It seems noise was coming from there. By holding a screwdiver to to bolt the noise was originating there. Idler pulley replacement did nothing to quiet the squeal. Belt looks good. Belt dressing spray does not help.
What is the next step reccommended to solve this problem?