I have a 1989 F150 with the 300 engine. The engine suddenly started getting loud. Eventually, the serpentine belt jumped off. I noticed the noise went away with the belt off. I replaced the belt, and the noise returned.

With the belt off, I can grab the fan blades and move the blades back and forth toward and away from the engine. Is this a sign of a bad water pump?

thanks.

 

If the fan blade is moving back and forth (respective to the engine) then, most likely your water pump is shot.

 

If it's the water pump, careful, I've had those things seize up so bad, I couldn't start the vehicle...


Have you tried the old dowel trick? Take a broom handle/dowel and touch the suspected part, place the handle to your ear and you'll definately know when you hit the noise maker