Mexstan

For about the last 2,000 miles I have a squeal coming from the front of the engine. It started as a small squeak at once per belt revolution. It was louder when the grid heaters kicked in. Also, something is chewing up the outside of the belt. By the outside, I mean that I have lost one complete rib of the belt. Installed a new belt and the same thing has happened in less than 1,500 miles. Slowly but steadily the noise is increasing and is now almost continuous, but often disappears completely once I have driven for about 10 miles or so.

Here is what I have done so far to trace the source of the noise:
Removed the belt about 6 times and spun every pulley looking for any wobble, noise or misalignement. Installed a new tensioner assembly (with pulley), removed the alternator and spun it up on a test stand (no noises) and regreased the idler pulley. Nothing I have done so far has made any difference to the noise.

This morning I removed the belt once again and it sounds like there may be some rumbling from the fan when I spin it. The fan is a bit of a pain to remove, so am asking if anybody has done it. What is involved in changing the fan bearing? Can a bearing be changed or do I need to buy some sort of assembly? If so, will places like NAPA have it? Do NOT want to go to the dealer. I am on the road and have some tools with me, so can do some work myself.

Any and all suggestions will be much appreciated.

Mr Jerry

I would have to think if it changed when the grid heater was pulling power off the Alernator,,,I would be checking the Alternator for bearing problems,,if the bearings are getting bad then alignment would be chewing the belt possably,,,might pull the belt again and check for slop in the Alternator shaft.

Jeff in TD

Also, there was a TSB for 03's regarding the stamped alternator bracket cracking.

It happened on my 03, and they replaced it with the updated part.

Lastly, there was a TSB regarding installing an over-run clutch on the alternator, to keep it from chirping the belt during shut-down and improve belt life.

Mexstan

I was there when the alternator shop checked the alternator. There is zero sound coming from the alternator when it is spun up and there is zero slop or end play in the shaft. Have positioned myself directly over the alternator pulley when the grid heaters come on and can't see any pulley movement.

Have had the new bracket for years.

I am aware of the TSB for the chirp, but don't think is the problem. Have had zero problems since new, but this problem has just recently developed.

If I am really energetic tomorrow morning I may pull the fan bearing out and take a close look at it.

Jeff in TD

You might also put a straight edge across the various pulleys as one might be slightly out of line that you can't otherwise see.

Mexstan

That is easier said than done. I have eyeballed all he pulleys numerous times from every angle I can conceivably get my eye into, but everything looks straight. If there was something out of line I would expect the squeal to be constant and not vanish when everything gets hot.

I am pretty good at troubleshooting most kind of problems, but this one is my nemesis so far, but WILL beat it.

bradler

paint/mark all the pulleys. you can use yellow or some other bright color spin and paint all the pulleys and the belt will wear the paint off where it is rubbing. that way you can easily see which side of which pulley the belt is rubbing on....

Mexstan

I know already that the belt is getting chewed up on the forward edge. On this belt as on the last two belts, have lost one rib or chord. Left this belt on with the one chord missing and so far it is working fine - except for that mysterious squeal. Positioned the belt with the chewed up edge away from the pulley edges, but the intermittent noise is still there.

This morning I lifted the fan out to do a close inspection of the fan bearing. Never removed the bracket, but just spun the bracket around the fan once I had it out. It spins smoothly and with no noises, which hopefully eliminates that as the source of the noise as the dealer wants $245 just for the bearing!

Not much choice but to continue my trip and hope that nothing dies while driving.

steelblitzkrieg

The paint idea is a good one it will tell you which pulley is chewing the belt.

Do you have access to a stethoscope? That's how I've seen mechanics check for noises in the engine compartment when it's hard to discern location.

My guess...A/C Compressor, I've had 2 intermittently squeal for some time before finally locking up on my 2002.

Mexstan

Have a stethoscope and used it, but it does not pick up anything unusual. Will try the paint thing after I get home.

cincydiesel

Stan, have you checked the tensioner pulley? I found out mine was bad when I found a piece of belt wound up in the fan after hearing some weird noises. I originally planned on just replacing the belt but once it was removed, I noticed the plastic on the tensioner pulley was melted causing the belt to wear a tear in it. Replaced the tensioner and belt and all was good.

Mexstan

Replaced the tensioner pulley and belt about a year ago as part on my preventive maintenance. it was the original pulley and was worn very unevenly, but made no noise or gave any indication of a problem. The new pulley still looks good, but a few days ago replace the entire tensioner assembly which has a new pulley on it, so that totally eliminates the tensioner or pulley as the source of the noise.

MR. GADGET

I had something kick up and put a nick on one of the pulleys, think it was a rock on the 96 and the ding or nick cut one of the ribs off the belt and made a ton of noise.

Jaxondad51

At the risk of sounding stupid, what is a TSB, and an over run clutch?

steelblitzkrieg

Technical Service Bulletin

Overrun clutch was a redesigned clutch for the A/C compressor or Alternator (can't recall which), when the truck would be shut off it would stop immediately causing the belt to slip and chirp, the overrun clutch slowed to a stop after engine shut off.