I have a 90 F150 3006cyl and 5 sp. Just recently the water pump went out so I replaced it. While I was there I went ahead an added new thermostat, hoses, and belt. When I finished I acquired a new squeel, sounded as if it was coming from the alt., so I checked it. It was not charging so I replaced it as well. Squeel still there, but only if the alt. is loaded up, say if runnin the heater and or headlights. After the gauge is in satisfactory position squeeling stops, but if the headlights or heater is runnin squeel comes back. The squeel is coming from the alt. direction, or smog pump. My thought was belt, but it is the correct belt. Any help...

 

Your tensioner may be worn out. A belt usually squeeks when is isn't tight enough or it is worn out. Since your belt is new it is probably not tight enough which leads me to think the spring in the tensioner is bad or, possible, you bought the cheapest belt you could find.

Chris

 

Make sure you have a good belt on it , like a goodyear gatorback , remove the belt & check all your accessory pulleys to make sure the turn freely....Lew

 

I'd go for the gatorback too if you don't already have it.

 

Right,check belt tension,