I have a 98 f150 5.4 4x4 with a little over 100,000 miles on it. Lately there's been an intermitent chirping/squealing sound coming from the motor. First, I replaced the drive belt and it was still chirping. I then replaced the belt tensioner and it still made the noise. So finally I thought I had it figured out and replaced the two idler pulleys. I drove it around the block with no noise occurring, but when I pulled into my driveway, it started chirping/squealing again. It sometimes chirps/squeals when I start the motor, more often when I tap the gas pedal in park, and sometimes while driving when I let off the gas. Is it ok to momentarily run the motor without the belt so I can make sure it is the drive belt and its associated components? Or is there anything else I can check?

 

quite often the chirp is the old belt mixed with oil residue on the pulleys and belt. if you changed the belt, i would suggest wiping off the pulley grooves with a cleaner. i have used a spoonfull of gasoline on a rag. you might use acetone, etc. oil residue cause the noilse. do not use belt dressing, it is a contaminant on the wide belts.

 

You might also wanna try using a 150-200 grit sand paper and give every pully a good scuff. Replace the OEM belt with a Goodyear Gatorback, chirping will be gone.

 

Ok, this is what I've done so far.
I replaced the drive belt (with a Goodyear Gatorback), belt tensioner, and both idler pulleys. I scuffed all pulleys with 180 grit sandpaper and then cleaned all pulleys with brake cleaner and wiped them down.

And it is still chirping.

Any other ideas will be greatly appreciated.

 

water pump?