My wife and I were out in the '85GT a couple of weeks ago. I drove the car to a family function an hour or so away from home, it ran perfectly on the way out. We got into the car to drive home and the belt started squealing and wouldn't stop until I got the rpms up. It did this all the way home anytime the rpms dropped close to idle it squealed. I got home and parked the car for a few days until I had time.
Well, I have Rodney's idler on the car and have not had any squealing issues since installing it until now. I checked the belt tightness and it was fine, so, I decided that something must have leaked onto the belt. I decided out of laziness that I was going to try to clean the belt on the engine, I grabbed a can of brake cleaner and sprayed the belt while the engine was running. I shot the spray at the crank pulley until the belt squealled, repeating this several times. Been driving it for a week, not a hint of squeal.
I figure the water pump seal is my prime candidate as the source of the leak, I'll just have to watch it.
Maybe you guys/gals got some ideas.
I posted this because the brake cleaner idea could be of benefit to other belt squeal victims.
White 88GT 5spd
White 85GT Auto
White 99 F250SD 7.3PSD 6spd
1956 Ford 860 w/ Freeman Loader