Screaming belts, Batman!

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Screaming belts, Batman!

March 23, 2015, 10:16:05 am

We had a grand time this last weekend, but spent more of it on gravel roads than I thought we would. The only trouble with this was that the engine belts started squealing within minutes of stirring the dust up, and simply Would Not go away. Even after tightening all of them, even after trying to wirebrush them, even after driving home, they are still yelling, although now they only scream when pulling away from a stop. I've not had this problem on anything else I've dealt with. My plan is to replace all belts and clean all pulleys unless one of you wizards has a magic fix.

Re: Screaming belts, Batman!

Reply #1 – March 23, 2015, 10:21:28 am

Assume this is on a Caterpillar 3208 with manually adjusted belts, not a serpentine belt with automatic tensioner.

Yes, dust can easily glaze the belts and "polish" the pulleys. Might try taking some 220 sand paper and radially sanding the surface of the pulleys to give them a little more grip. Better than over-tensioning the belts.

But, squealing belts can also be a symptom of failing bearing in accessory or idler.

Re: Screaming belts, Batman!

Reply #2 – March 23, 2015, 10:23:18 am

Is it all, or the idler? Mine dids that until I replaced it. Acceleration. ?. Squeal... shift... to 2nd squeal.. then quiet.... now after replacing.. I just hear the bratt-grrrrooowwll of the resonator

Re: Screaming belts, Batman!

Reply #3 – March 23, 2015, 10:24:57 am

I had similar problem with our Tracker. I sprayed the pulleys with brake cleaner. Squeal stopped.

Re: Screaming belts, Batman!

Reply #4 – March 23, 2015, 11:49:33 am

I was told a long time ago to try WD-40 and have on a few occasions, It worked for me, sprayed the belt itself and it quit squealing,

Re: Screaming belts, Batman!

Reply #5 – March 23, 2015, 12:07:54 pm

Jay have you tried to adjust the belts from underneath? I used to use a hydraulic jack put a little tensionon on adjustment for the two belts that run up to the fan.

Re: Screaming belts, Batman!

Reply #6 – March 23, 2015, 01:35:31 pm

Quote from: Adam Byler – March 23, 2015, 11:49:33 am

I was told a long time ago to try WD-40 and have on a few occasions, It worked for me, sprayed the belt itself and it quit squealing,

WD40 will stop the belt from squealing but only because it now slips. Temp will go up and the belt will overheat, be damaged and not do the job it is intended to do.

Instead, if you can't immediately get the belt to the proper tension, use a spray belt dressing from a parts store. Makes the belt stick to the pulley, especially if it was glazed. Always best to tension it either with a tension gauge or tight enough so you can JUST turn it 90 degrees with your fingers midway between pulleys. A belt too tight is responsible for a high percentage of alternator bearing failures so there is a limit to a good thing.

Serpentine belts should not have any more cracks per inch than the number of grooves. Example: a 8 groove belt should not have more than 8 cracks per linear inch. Otherwise, replace them and keep a spare onboard.

Pierce

Re: Screaming belts, Batman!

Reply #7 – March 24, 2015, 01:49:20 am

On the 3208 Cat the offending belts ate the pair that go to the idler pulley on the passenger side of the coach. These belts drive the alt and also the air compressor. They are very hard to get tight enough. I have replaced many sets of belts on the 3208 cats. I always used the Gates belts.

Re: Screaming belts, Batman!

Reply #8 – March 24, 2015, 09:42:58 am

Exactly. ?

I used a pry bar, until my dad used a hole in the bracket to put a tighten bolt pushing against the ac compressors housing, tighten bolt, release.. worked for about 4000 miles, then repeat procedure.. wish I had a picture.. ingenious idea.

Re: Screaming belts, Batman!

Reply #9 – March 24, 2015, 11:19:53 am

Gates Green Stripe fleet belts cost a little more but work well. Doing a Google search will find mail order prices almost half of a parts store price.

Loose belts get hot and will stretch, slip more, stretch more, slip more...

Pierce

Re: Screaming belts, Batman!

Reply #10 – March 24, 2015, 11:22:18 am

Quote from: red tractor – March 24, 2015, 01:49:20 am

On the 3208 Cat the offending belts ate the pair that go to the idler pulley on the passenger side of the coach. These belts drive the alt and also the air compressor. They are very hard to get tight enough. I have replaced many sets of belts on the 3208 cats. I always used the Gates belts.

Plus one on the matched gates belts.

Re: Screaming belts, Batman!

Reply #11 – March 24, 2015, 12:41:19 pm

The alt/air compressor belts are pretty new, and this rig has a nice big fat adjustment bolt under the alternator that lets me put a scary amount of tension on them. but is stands to reason that those are the ones under more friction than even the fan belts. What I'll try next is wirebrush them and the pulleys, brakleen, re-tension and see do they settle down.
I have to re-park it today anyhow. I nosed it into the driveway because it was dark and I was dead tired...

Re: Screaming belts, Batman!

Reply #12 – March 26, 2015, 01:00:33 am

There is a bearing in those tensioners that can go bad. I had to replace the bearings in both the tensioners in my old 1981 Foretravel with a 3208 Cat. It's a piece of cake job with a press. Don't try to pound them out and if you take it to a mechanic who tries to pound them out you are in the wrong place.

Re: Screaming belts, Batman!

Reply #13 – March 26, 2015, 09:46:07 am

On my 1990 U280 with 3208T Cat, the tensioner is located on the alternator bracket, and is a nut on a long adjustment "I" bolt accessed from the top of the engine under the bed. Very easy and works well.

Re: Screaming belts, Batman!

Reply #14 – March 27, 2015, 01:22:42 pm

That does the altenator, but not the actual belts that do the drive to the alt. The actual drive belts run from the crankshaft to an idler on the passenger side of the engine to the pulley that the alt belt goes to. Those 2 belts are pretty short and have a lot of things to run.

Re: Screaming belts, Batman!

Reply #15 – March 29, 2015, 12:39:22 pm

The belts that were loose on my '91 3208 had to be tighten from underneath the coach. The adjustment at the alternator does not tighten the drive belts. When mine got loose, the alternator stopped charging. I have to keep a check on them.

Re: Screaming belts, Batman!

Reply #16 – March 29, 2015, 05:24:01 pm

I would use light oil or penetrating oil.........yea..they will slip a bit but after the petroleum product softens the glazed rubber, they will drive normally........the thoughts listed here about tightening the belts so much, will only wipe out a bearing in something. Sometimes a little antifreeze on a belt will make it squawk so make sure there is no coolant on the belts!!

Re: Screaming belts, Batman!

Reply #17 – March 30, 2015, 09:50:53 am

Well, today is wirebrush-loosen-then-retension-the-belts day, and hopefully the noise goes away. Because our trip down the coast to the Redwoods is coming right up!

Re: Screaming belts, Batman!

Reply #18 – March 31, 2015, 10:26:58 am

Fixed. The culprits were the pair coming off the crank and going to the curbside idler pulley, which, as has been mentioned, is not easy to adjust but a floorjack and a 2x4 does the trick. Every one of 'em got washed and scrubbed while I was at it.

Re: Screaming belts, Batman!

Reply #19 – March 31, 2015, 11:21:07 pm

Those are the ones that carry the greatest load and are the hardest to tighten. They are more noticeable when the alt is charging on high and building air. Glad that you found them and was able to get them tight. I have replaced many sets of belts on the 3208 cats in the foretravels. It takes a system if you are going to beat flat rate changing them.

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