I have slowly been fixing things on my old 97 F150, just to keep it running until I get a new truck in the spring

recently I started hearing a chirp on my engine, I thought it might be the tensioner so I replaced it, but that was not it, my idler spins smoothly (as well it should, replaced it last year) but I did notice that when I turn my alternator by hand I can just barely hear a squeak, barely, but I cannot feel anything in the bearings. The chirp when I start it is much much louder though, hurt your ears loud if the hood is up, and it continues all through the drive, it never goes away

so is it likely that the little squeak I hear when turning it at 10 rpmish by hand is getting that loud at idle? or do I have some other damned issue I cant see?

Check the AC compressor.

Is the chirp present when running the engine with the belt removed?

would that kick in with the AC off? it is winter now and I have not run it in months

just turn up the radio

my Dakota does this when the humidity changes, sometimes I spray some wd40 on all the pulleys

Did you replace the belt with the tensioner?

Which motor?  I seem to recall something in the 4.9 300 motor's timing set that would chirp or make a weird noise when it was time to change it.  If its a 4.9, carry on.  The whole truck will fall apart before the motor does.



ETA nvm.  the 4.9 has a direct drive gear system that makes a distinctive whine at all times.  

It does NOT chirp with the belt off

I did not change the belt with the tensioner, though I do have a new belt to go on, I changed the tensioner because it was so tight when I put a wrench on it to take the slack off it broke....  though the bearing didn't feel horrible on it, just the spring was seriously tight


the truck has 340,000 + km on it if that matters

4.6L V8 4x4

with the engine running, spray some water on the belt, if it stops squealing then its the belt.

As for the AC compressor, the pulley is always spinning, but the clutch only engages when the AC or defrost is turned on. Use the defrost in the winter to keep the AC clutch from seizing.

Try some dielectric silicone grease on both sides of the belt, and the sheaves might need cleaning. Make sure the tensioner is strong.



Has coolant ever got on the belt?