Well it all started with a slightly annoying little chirp under the hood. I've owned my 94 Disco for about three weeks now, and since I had some time today, I decided to remove the serpentine belt and have a look. The belt looks fairly new, if not brand new. I cleaned the grooves on all the pulleys and slipped the belt back on. Whatever I did made the problem much worse!! Instead of a chirp, it's a steady, highly annoying squeal. As soon as it cranks, it squeals. When the idle calms down to under 1,000 rpm, the squealing stops. Above 1,000 rpm, squeals like crazy. The fan clutch is good, I did all the tests to check it out. All the pulleys turn smoothly and don't seem to be loose. Only things I suspect at the moment are the tensioner, which spins well but sounds a little rough, and the alternator, which squeaks a little when I spin the pulley, but it's a very faint squeak. It's frustrating when you try to diagnose a problem and only make it worse.

 

An old trick is to use some chalk on the belt and see if it changes the noise. I did it when the motor was running and touched it to the bottom (grooved )side of the belt. Be extremely careful not to get caught in the belt, fan or pulleys. There might be a spray to dress the belt which would be much safer to use but I can't say if it would help.

 

Just try a new belt, you should be keeping a spare in the vehicle anyway.
If it goes away, it was the belt, if not, then it's something else. I would suspect the alternator bearing since it squeals a little turning by hand. It could easily be worse when the tension of the belt is on it.
Replacing the tensioner pulley bearing is cheap and pretty easy. You probably should if it's "rough" like to say.
SKF 6203-2RSJ

 

Only time mine spuealed the belt was routed wrong, easy mistake on these

 

Yeah, the nature of serpentine belts usually prevent them from squealing.

 

The belt is routed correctly, I made sure of that.
Tried the chalk on the belt, no change. If I put my ear close to the action, it sounds like it's coming from around the water pump. When I took the fan off before and tried to "wobble" the water pump pulley, it didn't seem to have much play. Could it be as simple as a bad belt, even though it looks practically brand new?? Don't really have the funds to replace the water pump at the moment

 

Yup I had the alt done (to busy to do myself at time) belt squealed replaced belt, tensioner bearings, then tensioner, then I realized they misrouted the belt sucks cause I threw out a gatorback belt

 

You should have ran the truck without the belt for a bit to see if it squeals without the belt. That would tell you if its belt/pulley related for sure.
Now that your belt is back on, take along screwdriver, broom handle, stethescope, etc and stick one end to your ear and the other to a pulley. Move the business end of the stick around from pulley to pulley, part to part, until you hear the noise the loudest. You've now found your problem.

 

Forgot to mention,I ran it with the belt off. No noise. Also I did try listening with a broomstick. Maybe I'm not sure what to listen for, but everywhere I put the "business" end, all I could hear was the pulley rubbing the stick.

 

I got the squeal to stop!! Not sure if it's permanent yet, but here's what I did.
Took the fan off. Removed the belt. Rechecked all the pulleys for wobble, they all seemed ok, though I don't know exactly how much play is acceptable. Sprayed a little WD-40 on the tensioner bearing, and got it to spin very smoothly. Replaced the belt and cranked her up. NO SQUEAL, Hell Yeah! Like I said, not sure if it's a permanent fix, but maybe relieving the drag from the tensioner did the trick. I'll take it for now.