My daughter's car, 2004 Buick Lesabre 148K, runs like a top; I've changed serpentine belts numerous times, GM OEM #12569591, Goodyear Gatorback, Dayco, Bando, the old OEM belt back on....I have 5 belts, 4 of them less than 10K each. No matter which belt I use, it runs for awhile after being thoroughly warmed, then when you're idling like at a stoplight or in a drive thru, the belt starts howling like a banshee. It gets quiet upon slight acceleration, never a peep out of it on highway, etc.,A/C Compressor is good (per A/C only shop), water pump OEM new, belt tensioner new OEM, power steering pump smooth as butter....It's just aggravating. Tried belt dressing about 20K ago, no real help. Suggestions (other than dynamite) welcome.