Cant tell

can anyone tell me how the best way to tell which engine pulley is bad on a 2001 F-150. ive started by changeing the belt and it still sqweeks
thanks.

Listen and isolate the sound.

Use a Mechanic's stethoscope, but be very carefull not to get it (or your mullet) caught in the moving parts!

I bought one of these and use it quite often to diagnose belt noise, wheel bearing noise, and other squeaks and rattles.

A really long screwdriver butted to the ear also works, but it's hard to see with your head sideways!

Ah, edited your response already. I received e-mail notice of your response "Use a Doctor's stethoscope" and was going to suggest a mechanic's stethoscope would be better.

Because with the longer 'probe' less chance of a mullet mishap.

One can also use a long ratchet extension bar which transmits sound fairly well, using the female drive end as a sound bell.

hahaha alright thatnks guys ill give it a try