My 4.0 has a squeak. I've replaced the idler pulley and tensioner with no change. It sounds like it's in the front center of the engine.
Once everything warms up it stops, but until then it squeaks. No other pulleys vibrate or wobble and the belt is in good condition.
Not sure what it is. Fan clutch? Water pump ( hopefully it isn't that).

Any ideas?

 

I had that. It was fan clutch and my water pump was bad too.

 

Don't water pumps weep when they go bad? Is there a way to test the water pump and clutch? If the water pump does end up being bad, how easy is it to change?

 

My truck is under warranty. Ford replaced fan clutch for noise. A couple months later I noticed the weep hole leaking and they replaced that too under warranty.
I do not think the water pump is too bad to replace. Its right on the front of engine.

 

Is it maybe belt slip since you have replaced your tensioner and idler? Best way to find out if it is belt slip is to spray some wd40 on the belt to see if the noise goes away when running.

 

Yeah it was the belt. I changed it out yesterday with a Goodyear Gatorback. No squeaks this morning. The one I took off was a little stiff and glazed, but otherwise it looked fine.

I'm just happy I don't need to change the water pump!

 

I replaced the belt, idler and tension pulleys.
Still squeals in the morning.
If I sprinkle baby powder on it it stops the noise.
???

 

I have a squeak that only happen when I accelerate . As soon as I let off the gas, it stops immediately. Does yours do the same thing?