Need some diagnostic help. I have a 2001 F150 V8 4.6 2WD with A/C. Was having horrible squeaking noises, sounded like a bearing. I first replaced the idler pully, as I noticed a build-up of gunk on it. That did not fix the problem. I next went to the belt and replaced it with the Duralast belt. That fixed the problem for about a week, then the chirp came back. Then moved on and replaced the tensioner and pully. That worked for about 2 days, now the chirp is back, but not yet near as bad has it had been. I notice it most when running about 1200 - 1800 RPM but occasionally when idling, which is about 700 RPM. When I run the engine without a belt there are no squeaks, chirps, rattles, or any other abnormal sounds. All of the pulleys appear to be tight. The power steering pully has about 1/8" play straight in and out, but I was told that this is normal.

 

Welcome to the forum

Try a Gatorback belt, they seem to be quieter than most.
Also could be an alternator bearing making noise with the tension of the belt on it.

 

Also depending on age/mileage it could be the fan clutch. Mine squeled because the bearings inside were seizing up.
X2 on the Gatorback

 

where can you get a gatorback belt? any local parts store?

 

Autozone has them.

 

ok cool. cuz i get a belt chirp on upshift and when its damp every now and then.

 

bpd357 can try running it w/o the fan clutch fairly easily. The big reverse thread nut that detaches fan from water pump allows for the motor to run & all belt driven accessories to spin. I went through all the usual suspects w/o relief.

My 4.6 had "chirping and squeaking" that baffled the experts in my Dad's home town. It would chirp at idle & squeal when you accelerated the motor. I'd also suspected AC clutch & alternator bearings. The FORD mechanics were surprised after I discovered the harmonic balancer had shifted slightly out of line & it's pulley was rubbing the front cover on the motor. However the noise wasn't from this contact. The small misalignment (barely 1/8") was enough to cause the belt to act up, resulting in the noises.

Try spraying water on the belt. In my case water from a spray bottle would silence the chirping for a few seconds, confirming the noise was generated at the belt-not any bearing. The harmonic balancer looked perfect, but had slipped on it's core & crept backwards. Irregularities in the sand cast front cover made it difficult to judge the small gap at rear of crank pulley. It required removing the harmonic balancer for me to prove this. The pulley was rubbing against a high spot on the casting.