belt squeal - out of ideas...
 

hey guys, been lurking for a few months, but new to posting here...

i have a 00 limited with 130K 4x4 miles on it.

problem: under load when cold, i get a high pitch squeal around 4000rpms. once warm, no squeal other than a faint rattlesnake type sound under load or going up a hill.

what i have done: replaced pully, tensioner, alternator and belt.

I still get the noise, and i cant really figure out how to troubleshoot where its coming from now. there are only a few other area where i could thing, water pump bearing and a/c bearing.

Any other ideas of what i can do to troubleshoot? or maybe i'm not in the right area at all?

Clean all pulleys with brake cleaner and a wire brush. If they were oily, you might need another new belt. Everything is turning harder when it's cold, the alternator is working hard after some parasitic draw overnight and starting in the morning, and the fan pulls harder the faster it's turned. Sometimes you get a bad belt, maybe your parts store will take it back and exchange it. Take the belt off and spin everything by hand, listen and feel for bad bearings.

I would double check the pulley alignment also. A straight edge is helpful for that.

use some belt conditioner.. it comes in a can and works great to stop squealing, although what is 4000 rpms... mine lives between 1500 and 2500... u must be one of those gas guys.:-)

How is the idler pulley? If you feel or here any crunching when spinning a pulley they are bad. What kind of belt did you use and what engine? Assuming 5.4 or 6.8 V10.

crazy that I didnt even write it in the post before... it is a v-10. for some reason i thought all limiteds were v-10.

i only get up to 4000 rpms when accelerating. mine lives at 2100rpm unless its under load, which is only when it squeals.

I've replaced the tensioner and pulley, are there more than one of each?

the noise hasnt changed a bit even after replacing all those parts. I'll try a few of those things and get back to you.

Have you removed the belt and try to duplicate the noise? If the noise is gone without the belt but comes back when you put the belt back on, that confirms it is something running off the belt.

Look at the belt alignment at the ps pump. The pulley may need to be repositioned.

Also look at the edges of the belt for shinny spots that can indicated a rub.

When I did my harmonic balancer you had to press on the new balancer so that it kept the belt in lign... If you pushed it on too far it would tweak the belt a little and Same if not enough... I think he is on the something with belt alignment.. If the pulleys have all been replaced then I'd go that route

4,000 RPM cold?

Besides this (WTF?) I thought about a similar sound that I had and could not
verify it. It was an exhaust blowoff due some leaks at the headers.
I tighten all bolts and add 2 missing ones and voila it never pop on again.
Maybe you check this before you throw some more money on it.

I have seen a bad clutch fan grab harder when cold. Those put a heck of a load on the engine. Do you notice if your fan is trying to go 4000 rpm with the engine when that's happening?

ok, i finally have an update on this.

I had the right side exhaust header bolts taken out. 8 of 10 were fine...2 were broken in the head. with that fixed, the "belt squeal" is now gone...which is funny because i took it into the shop to fix the "rattlesnake" noise fixed.

But the rattlesnake noise still exists and I am thinking it is more from the exhaust underneath, maybe from the cat converter? sounds like a baby rattle under some load sometimes , and doesnt make a noise at idle.

Remove the cats and/or the heat shields. Lay under and bang on things to see if something rattles.

thanks, i was just searching the site and came across laying under it and pounding with a rubber mallet. i'll report back.

still amazed that squeal was from the exhaust.

well, i was under there friday pounding away. thought i found it was the shroud on the muffler, took that off, and the muffler was falling apart, but intact. Had it replaced and still have the noise, just a bit more "tinny" sounding than before.

today, it is at the shop. his best guess is it is not the cat. but further up, maybe still a problem with the exhaust header....