My 2004 5.4 F150 has a high pitch squeal only in cold weather at about 2000 RPM. It goes away at higher and lower RPM. It must be cold outside - below 30 deg. It does not go away after warm up. Continues on long trips during winter but it fades in and out. There are no other symptoms tied to it. Just noise. It's been with me during winter for a few years now...

Any ideas?

 

My 2004 is exhibiting the same behavior. Some of my research points to the alternator or the idler pully. It is warm now so I have put it on the back burner.

 

this is a known problem with the earlier trucks, I believe it's the alternator. My '05 has done it since day one and i've never had anything fail, it just can be a little annoying in the winter.

 

Same here on my '05, only when it's below freezing, it goes away after it warms up also. My plan's to move to a tropical oasis to fix this problem.

 

i really only notice it when the temps are single digits or below. when it starts making noise I either slow down or speed up a little to get out of the RPM range that it makes the noise.