Squealing fan belts - what's the cure?

[Guest imported_TheColossusofRoads]

A while back the fan belts on my '85 LeSabre began to squeal and screech when the car was first started up. After 15 seconds or so the noise would go away, and was OK while driving, until it sat for a while (like overnight)and then it would do it all over again. I replaced all 3 belts, and the problem is back. The pulleys look shiny, but are not coated with anything foreign or cruddy looking. The car has 251,000 miles on it and I've never had this problem in 15 years of ownership. Anyone have an idea as to what to do next?

Thanx.

[Guest Dynaflo2]

Since you have already replaced the belts, I would suggest you check belt tension and alignment of the pulleys. Do the pulleys all spin freely? I once had an A/C compresser sieze up on me and boy, did the belt squeal! Does it ONLY squeal when cold? What about hard acceleration, sharp turns, etc. Looking for anything that would put an extra load on a given belt. Can you isolate exactly where the squeal is coming from? To isolate the source of a sound under the hood, try cutting a short piece of 1/2" PVC pipe (a foot or two) and putting one end to your ear and pointing the other to various parts of the engine. (<img src="http://www.aaca.org/ubbthreads/images/graemlins/ooo.gif" alt="" /> BE CAREFUL! <img src="http://www.aaca.org/ubbthreads/images/graemlins/ooo.gif" alt="" />) It works like a directional microphone and makes it easier to filter out all the sound-bouncing that goes on under the hood. If that doesn't help, squirt one belt with belt dressing and see if that one is the squealer. If it isn't, try another to see if that one sqeals, then try the third. As a stopgap, you can just go with the belt dressing, but that only masks the problem. It doesn't fix it.

[Dave@Moon]

The best tool to use to find problem noises is a mechanic's stethoscope. Harbor Freight Tools sells one for about $5. I use mine all the time. It's amazing what it can tell you about bearings. valve trains, etc.

[Guest imported_NikeAjax]

There is a spray that you can buy to spray your belts with; sorry, I can't remeber what it's called. Also you might check to make sure your alternator belt really is tight, but not too: you should be able to get about 1/2 inch when you press down on it. Io have found that alternator belts get super loud when they're tight enough.

Good luck!

[critterpainter]

Start with the Alt pulley and then try the crank pully...sand the shieve (pulley) with course sandpaper to give it some "tooth" squealinig is caused by slipping which in turn is caused by either glazed belts or worn or polished pulleys. with high milage look at the pulleys

[NTX5467]

From my experience with my '77 Camaro 305, some engine combinations just seem to have belts that will alwasy be a little noisier than others, even with the same part number pulleys. Most every 305 Camaro/Firebird from my year had some belt noises that could not be made to go away, but the same pulleys on a 350 were always quiet. BUT your car is not one with cronically noisey pulleys.

Of course, the "clean" thing is necessary and scuffing the pulley sheaves might help (but don't get too coarse as it could affect belt life). Typically, when ever you put on a new belt, it will need to be run a little while before the final tightening will need to be done. In other words, that new belt will get a little more pliable after it runs for about 45 minutes or so. In some cases and some brands, the extra stretch in the belt after installation can be significant enough for it to really squeel. After it squeels for a while, it can then glaze the belt and it'll make noise that you can't adjust out.

WD40 can soften the rubber in an older belt to temporarily make it quieten down, but it and other treatments will only be temporary and usually work best with older and more aged belts rather than new ones. Some treatments can cause more trouble than they're worth too.

So, after you put on a high quality new belt, tighten it to what seems right (with no more than about 3/8" play between the longest length between two pulleys), and then run it a day or so through several hot/cold run cycles. After that's happened, then if you recheck the play in the belt (with the engine stopped, of course!!!) or look for flopping while it's running at idle, you'll see a slightly loose drive belt in all probability. Then, readjust the tension on the belt and it should stay where you adjust it for the rest of its life. If you put too much tension on the belt, it can also affect the life of the bearings in the particular units the belt is driving too, so don't try to make them piano strings or similar.

After that, if there is still some squeeling on particular belts, you might consider seeing why that particular accessory unit might be putting too much load on the belt.

Hope this helps . . .

NTX5467

[Jyrki]

I'd say it's the alternator pulley. Being small in diameter, the belt will eat into the metal, until it eventually bottoms out in the V-groove. When this happens, there's no cure other than a new pulley or a completely new alternator.

We are talking about V-belts, aren't we? The alternator belt squeals right after the start, when the load is greatest. You might also try swapping a bit wider V-belt to prevent bottoming out.

Edelbrock sells a gasket sealer called GASK-A-CINCH, which can be used as a belt dressing. Might be worth trying.

[NTX5467]

In many cases, GM was known to use a 3/8" wide V-belt in production and then do a number change "in service" to a .440" wide belt. When that change was made, I found it necessary to increase the length on the orig thinner belt by 1 inch as the wider belt would ride higher in the sheave than the more narrow belt. There are also 1/2" wide V-belts, but I don't recall any applications for the vehicle you have.

On some of the Cadillacs of that general vintage that had the 100 amp alternator, they used a smaller diameter pulley to keep the alternator speed up a little. In this application, they specified a notched belt so it would better conform to the smaller pulley--a non-notched belt would squeel as it would not successfully make the turn on the smaller diameter pulley. This might be an alternative too.

Hopefully you are using a quality brand over there. You might need to convert the 3/8" and .440" widths to metric, but I suspect you can find something acceptably close to what we had over here.

Enjoy!

NTX5467

[Guest imported_TheColossusofRoads]

I think I have found a cure - at least for the moment. We'll see how long it lasts. I loosened the A/C - air pump belt to check if the A/C unit was binding, (the A/C hasn't worked in quite a while anyway) as one writer suggested. It did spin freely, so I re-tightened the belt, perhaps a bit more snug than it had been.

Also, I sprayed some PPG Acryli-Clean wax and grease remover in the "v" of the pulleys and let it sit for a while. After it did it's thing the glossiness on the pulleys was pretty well gone, and the belts haven't squealed for two days now. (With 251k on the engine, there probably was lots of goop fused to the pulleys). Maybe this did the trick.

Thanks to all who took the time to offer help - It is appreciated.

RB