How do I stop a squealing fan belt?

In May while I was driving from Yuma to the Grand Canyon I stopped in Prescott to have my alternator and the fan belt replaced. Then I continued on to the canyon. The next morning I discovered the fan belt squealed when I started up the engine cold. After about a minute it warmed up and stopped squealing. So I bought a can of stuff to spray on the belt to stop it from squealing. But a week later it was back to squealing. I found a mechanic at the canyon and paid him to tighten the belt and it stopped squealing for a while, but then started to return.

A month later I was driving from the canyon to Las Vegas and about 15 miles from Kingman the fan belt broke and wrapped itself around the fan. I got towed to a RV repair shop and had the belt replaced. The next morning it was still squealing when cold. I tested the belt adjustment and it felt fine to me. I took it back to the place that replaced the belt and the mechanic agreed with me that the belt was adjusted properly. He looked and found a small leak of antifreeze coming from the lower radiator hose that was leaking onto the belt. A very very small leak. So I paid him to replace the hose. It still squeals when it is cold. I have heard that using the belt squeal stopping spray is not really very good for the belt.

So what should I do to stop this stupid squealing?

check to see if the pulleys are lined up

Stop at a TractorSupply and get some belt dressing spray. I used it for years on squeaky belts on my combine and never seemed to have any trouble. The combine had at least a dozen different belts on it.

A quick fix would be to hold a bar of soap against the belt while it's running. Just be extremely careful where you have your hands and don't wear long sleeves while you do it. The soap will clean the anti-freeze from the belt but a loose sleeve around a running engine can be very unforgiving.

Tom,  you need to check to make sure everything is turning free. Normally after a cold start the belt squeals because the alternator is trying to produce a lot of amps to make up for those used in starting, otherwise a high output to put the charge back in the battery. SHould it squeal, no if everything is right and you have a good quality belt. I have used belt dressing and soap in the past and they do work for awhile but is not the final solution.

Check the alternator bearing, the water pump and anything else that is operated by that belt for resistance and bearing looseness.

It may be they did not use the correct belt.  A small difference in length can be accommodated with adjustments, but there is also the profile (shape) of the belt to consider. Not all V-belts have the same "V", and some belts have different profiles altogether. There are grooved belts, teethed belts, etc. It is not all that unusual for a mechanic to "make do" with a belt he has on hand rather than waiting to get the right one form the parts house. Especially on a motorhome, where shops often try to substitute a belt that would be used on that engine if it was in a pick-up truck or van.  Those often are not the same.

You might buy another belt for your  chassis and see if it looks the same. But be sure it is the belt for the motorhome chassis and not a car or light truck.

Belt "dressing" may be the quickest, easiest and cheapest soulution to you problem.

Gary RV Roamer said:

It may be they did not use the correct belt.

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That is possible but it has happened with two different belts.

Check to see if the alternator pulley spins free without the belt on it, and also watch carefully to see if it "wobbles" as you spin it.  If it's not aligned on the alternator shaft just right, it can wobble a little as it spins and this might cause your problem.  Also, if whoever rebuilt the alternator did not replace the drive bearing, it might be worn. Check this by grabbing the pully and try to pull it perpendicular to the alternator shaft and see if there is any play.  Also spin it slowly with your hand on it and make sure the shaft is turning smoothly.  This will also be an indicator of bearing condition.  Also, the pully on the engine should be perfectly aligned with the pully on the alternator.  The belt dressing is not a permanent "repair" it's just something to use to isolate the problem.  I don't think your installation has a belt tensioner, but if it does, they can squeal also, prior to failure. If you have one of those, back it off of the belt and use the same procedure as above to check it's bearing also.

Tom,

It may well be a bearing problem if you do have the correct belt. Both the alternator and the idler (if so equipped should turn freely when the belt is loose. Like with one finger. If they don't (and I'd think the mechanic(s) will have checked this by now); you might have gotten a larger alternator than the one replaced. Alternators put out a large amount of current just after starting because the battery has been pulled down by the starter. If you have a larger alternator, it takes more to turn it during this period (that's why belts squeal on start up). To summarize the possibilities:

a. Belt may be loose - usual problem.
b. A bearing may be seized or starting to seize - common with older parts.
c. You might have the wrong belt.
d. Lubricant on the belt - oil or antifreeze.
e. Pulley or alternator misaligned - wrong alternator or pulley not installed correctly when alternator replaced.
f. Just a higher output alternator than the belt is designed to run.
g. Its gotten harder to start the MH, causing the battery to be pulled down further (or weak battery).
g. Murphy is here!!!

I've seen everyone of these!

Hope this helps,

Ernie

Ernie n Tara said:

f. Just a higher output alternator than the belt is designed to run.
g. Its gotten harder to start the MH, causing the battery to be pulled down further (or weak battery).

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I was in the process of mentioning this and my power went out.  Oh well, great minds...  But, put these two together and the load could easily cause a belt to squeal even on an otherwise perfect system.

And then again, it may just be the residue from the anti-freeze leak that he mentioned was found. Any kind of oil on a belt will cause a squeal. Be interested in what's found.

That is possible but it has happened with two different belts.

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Aha! That points to a different problem then. You had previously indicated the squealing began when you had the alternator and belt changed.

Gary RV Roamer said:

Aha! That points to a different problem then. You had previously indicated the squealing began when you had the alternator and belt changed.

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How does that change anything? The problem started when I had the alternator and the belt changed. That belt broke and I changed the belt and the squealing continued.

seilerbird said:

How does that change anything? The problem started when I had the alternator and the belt changed. That belt broke and I changed the belt and the squealing continued.

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This has been mentioned in a way, but is your new alternator a higher output alternator than the one you had replaced?

Gary RV Roamer said:

It may be they did not use the correct belt.  A small difference in length can be accommodated with adjustments, but there is also the profile (shape) of the belt to consider. Not all V-belts have the same "V", and some belts have different profiles altogether. There are grooved belts, teethed belts, etc. It is not all that unusual for a mechanic to "make do" with a belt he has on hand rather than waiting to get the right one form the parts house. Especially on a motorhome, where shops often try to substitute a belt that would be used on that engine if it was in a pick-up truck or van.  Those often are not the same.

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what he said.

AND, its only crank alt and fan?  is the fan locked up?  that'll snap belts pretty good as well

I don't know if the new generator is a different output than the old one. I didn't request a different output so I don't think they would have used a higher output. The fan is not locked up. The fan turns freely and the fan thermostat works as it should. If the fan was locked up I would have lost a lot more than one belt.

Sometimes a replacement alternator is supplied with the wrong pulley. Check to see if the pulleys are the same width and are perfectly aligned. If so use a piece of emery cloth to take the shine off the belt groove, then clean them all real good with brake clean. Clean the belt with brake clean or a good detergent. Make sure everything is completely dry then put belt on and tension it. After you warm it up retension the belt.  Belt dressing usually causes the belt to slip and glaze the pulley.  Never ever put belt dressing on a serpentine belt.

Just a thought that is a bit of sideways thinking to this immediate problem.  When the mechanic tells you a belt needs replacing keep the old belt just in case.    This way if you are outside a major centre you have a spare belt.  (I'm thinking of visiting Wollaston Lake, Saskatchewan to visit a family member who works up there in summers.    It's within 50 miles of the NWT border and on the other end of 300 miles of gravel road.)

However do not assume that old belt will last very long.  Rubber belts age just like tires.  (But when they fail they tend to not cause as much damage as RV tires.)  So as soon as you can get near a major centre purchase and install a new belt.

Being the paranoid pessimist that I am, after, a number of years I'd be quite tempted to purchase a new belt and have it installed anyhow when on a mechanics visit.  (Which I have done in the past.)  And cycle out the real old belt.

The mechanic did not tell me I needed to change my belt. I did it because I don't change an alternater without changing a belt. I should carry a spare fan belt, but there are dozens of other items I should be carrying but since this rig has no basement and very limited storage carrying a lot of spare parts is not an option. A good idea though Tony and thanks for the thought.