Have 2004 F150 xlt supercrew 4x4 problem is loud high pitched squeal in engine bay towards the front. Could this be waterpump going out? I have no heating or cooling problems. Belt also looks fine. Alternator is working fine. This occurs mainly at start up and acceleration. After a short drive it quiets down quite a bit. Last night it was the wost it has been. Weather was 50 F and rainy. The pitch of the squeal changed a little when my wife turned the dash heater ***** from vent to defrost. It was real loud like a hay baler. If any one can help with this diagnosis I would appreciate it!

 

that would be the airconditioner compresor causeing the belt to squel.
need to check that out. the reason is the a/c comp. comes on with defrosters

 

Vacuum leaks can be quite noisy...my old truck with the 300 got a leak in one of the HVAC lines and it whistled loudly enough to hear over the radio while driving.

Have the motor idling, pop the hood, and get a length of tubing (doesn't matter what kind, just small enough so you can place it right next to your ear. Hold the other end of the tube and wave it near possible sources. A/C, alt, idler, tensioner. If one is making noise you'll know it.

If it's a pulley get a can of wd-40 and spritz it on the suspect one. If it stops for a few seconds and then gradually returns you've got a bad bearing.

Get a helper to turn the a/c on and off while you listen. If the squeal starts/stops accordingly then you've got your culprit. If it squeals all the time but comes from the a/c, the clutch is going.

 

Right , you have to set it to "vent" if you don't want it to run :santa:

 

You sure it's not just a worn belt screaming?

 

Checked belt and seems fine. The ac switch works fine also not automatically kicking on like my wifes Focus does. I'm thinking its a bearing due to being quite now at the start then starts squealing and getting progressively louder. Still open to any other tips or suggestions.

 

I'de have to say idler bearing then..

 

prbly so

 

x2

Even if the belt "looks" good it can often be bad. Start it up and hit the belt with a quick shot of wd-40 and see if it goes away. If so the belt is bad