My 78 has had a "squeel" in it for several months. It comes on at about 2200 rpm, and then quits at about 2500 rpm. I thought it was a loose fan belt, but I have tightened them and there is no change in the noise. There are no leaks at the water pump or the power steering pump, and the alternator charges OK. There is a small diameter idler pulley that is mounted next to the AC pulley, could this be it? Any opinions are welcome. Thanks.