Fan belts squealing - can’t seem to solve

[AR67GTX]

My factory AC/PS 67 GTX fan belts are driving me crazy. The belts are all new Dayco Top Cog belts. They howl just like the others I’ve tried. I’ve made sure the pulleys are all aligned via straight edges and wood dowel rods laid in the grooves, to perfection, adjusting any that were not. I’ve tightened the damn things to were there is almost no deflection. Drive along at any speed, in any gear, and just give it some gas and it howls away.

I don’t think it’s the AC belts since they are doubled up. I bought 3 to pick the closest 2 but they were all well matched. Also the screeeching doesn’t matter with air on or air off. I believe years ago I removed them for a test w/o any luck, it’s been so long I don’t remember everything I’ve tried. I have a hard time believing it’s the PS belt as it has 180 degrees purchase on both pulleys, but not sure. That leaves the water pump and idler drive belt which has more like 140-150 degrees purchase on the pulleys. I believe this is the problem belt - but not 100% sure.

What to do? Do I need to sand blast the pulley surfaces? None of them appear real slick but kind of hard to always tell where the belt is riding in the groove. The water pump idler pulley used to sit a little crooked but I worked on it some years ago and got it straight - I can’t even remember what I did to it I’ve been fighting this so long. Anybody got any ideas on this?

 

[pnora]

I would try to isolate it. Run it with the a/c belts off and see what happens. If it does it right away on a cold engine you could then try it with the a/c belts on the the WP belt off.

 

[gtx6970]

Do it with or WO the ac on will narrow it down
Not likely its the idler belt as it has no real draw to it persay UNLESS the water pump is to tight
I fought this same thing several years ago on different car

Take rough sandpaper to one belt at a time, go for test drive see what happens

 

[ruffcut]

I think you're right. Not the belts as they are aligned and new. I'm thinking it must be a pulley. Call me crazy but I'm leaning toward the water pump pulley but could be the bottom pulleys too. I hear what you're saying about the squeal driving you crazy. My old truck was doing the same for years and finally fixed it by changing some pulleys. Good luck.

 

[AR67GTX]

Do it with or WO the ac on will narrow it down
Not likely its the idler belt as it has no real draw to it persay UNLESS the water pump is to tight
I fought this same thing several years ago on different car

Take rough sandpaper to one belt at a time, go for test drive see what happens

Bill, AC on or AC off has no effect on it at all.

 

[AR67GTX]

I would try to isolate it. Run it with the a/c belts off and see what happens. If it does it right away on a cold engine you could then try it with the a/c belts on the the WP belt off.

I may be forced to do this again. I’ve been working on this for 10 years plus and pulled belts off, changed belts, etc - that I can’t remember what I’ve done and the results anymore. Pretty sure I had it down to the PS or WP belt but may have to recreate my past work.

But, once pinned down for sure, what the correction? I tried some belt spray many years ago but it was short lived.

 

[Bird 426]

Two things, is that a cogged belt? Second, if a belt bottoms out in a pulley groove, it will never stop squealing. A/C belts were solid matched belts. Don't believe they are available any longer.

 

[Sixpactogo]

I've had an idler pulley bearing squeal like a belt slipping. Are you sure that is not the problem. It looks like you are back to square one. Drop one belt off at a time until you find the culprit.

 

[AR67GTX]

Two things, is that a cogged belt? Second, if a belt bottoms out in a pulley groove, it will never stop squealing. A/C belts were solid matched belts. Don't believe they are available any longer.

Not on the bottom, clogged on top. I use stock width belts but I’ll look at them closer to see if any look that deep into the groove. Dayco’s seem to run a few thousands wide.

Thanks.

 

[AR67GTX]

I've had an idler pulley bearing squeal like a belt slipping. Are you sure that is not the problem. It looks like you are back to square one. Drop one belt off at a time until you find the culprit.

No, I’m not sure - it’s the same idler that was on it when I bought it 25 years ago. About 12-13 years ago I had a strange deal where it ate the water pump belt in two. I mean literally. When I picked up the belt an entire shallow, arc area had been ground out of the belt like it was being held stationary until a spinning pulley actually wore clear through it. I got another belt at a nearby store and before I even got out of the parking lot it did it again, rolling all the other belts off in the process. I had it towed home and I pulled the water pump to examine it in case it was seizing up but found nothing wrong. I put a new one on it anyway and new belts and it’s been OK since - except for squealing. But I’ve never felt comfortable taking the car far from home since then.

Looks like I need to go through pulling the belts one by one again which is a pain because the AC belts are on the outside. I may look for another idler bearing too, although I would think if a bearing it would be rpm sensitive. I can ease up to highway speed fine but at any speed just goose the throttle a little and it squeals.

Thanks

 

[copper67sat]

I've had an idler pulley bearing squeal like a belt slipping. Are you sure that is not the problem. It looks like you are back to square one. Drop one belt off at a time until you find the culprit.

I have the same belt setup on my 67 383 with PS and A/C. I had to replace the idler pulley several years ago because it started making a noise that sounded a lot like a belt squealing. Checking the belts, I noticed that the idler did not turn smoothly - the bearings were going bad.

 

[AR67GTX]

I have the same belt setup on my 67 383 with PS and A/C. I had to replace the idler pulley several years ago because it started making a noise that sounded a lot like a belt squealing. Checking the belts, I noticed that the idler did not turn smoothly - the bearings were going bad.

Thanks - I’ll check it tomorrow.

 

[Mick56]

Let the belts squeal for a minute, then shut off the engine and quickly touch each pulley. The offending pulley will be very hot.

 

[AR67GTX]

Well, it was the PS belt as suspected. Which was good as it’s the outside belt. Don’t know why I was thinking above the AC belts were outside. Took the idler off and it looks pretty new and is tight and very smooth. Checking alignment on the idler again it looked like it could still stand to come out 1/32 - 1/16” so I found a couple shim washers to do that. I also cut a long, thin strip of blister pack plastic and slid it between the belt and the pulley in the groove to verify none of the belts are bottoming. Tried it again and still squealing.

Took the belt off again and sprayed it with belt conditioner and set it aside and worked at sanding the pulley grooves with a piece of coarse sandpaper. I got the idler pulley and water pump pulley pretty good. The balancer pulley was hard to get to but I managed to secure some sandpaper to a length of vacuum tubing and drag it around it kind of like polishing a crank journal. At least got most of it roughened up a little. Put the belt back on tightened it up and tried it and it’s stayed quiet for a test drive and a couple of short acceleration pulls. So fixed for now but not sure it will stay that way. If it starts again I’ll sand the pulleys some more.

Thank for the ideas.

 

[Rebelrouser]

My factory AC/PS 67 GTX fan belts are driving me crazy. The belts are all new Dayco Top Cog belts. They howl just like the others I’ve tried. I’ve made sure the pulleys are all aligned via straight edges and wood dowel rods laid in the grooves, to perfection, adjusting any that were not. I’ve tightened the damn things to were there is almost no deflection. Drive along at any speed, in any gear, and just give it some gas and it howls away.

I don’t think it’s the AC belts since they are doubled up. I bought 3 to pick the closest 2 but they were all well matched. Also the screeeching doesn’t matter with air on or air off. I believe years ago I removed them for a test w/o any luck, it’s been so long I don’t remember everything I’ve tried. I have a hard time believing it’s the PS belt as it has 180 degrees purchase on both pulleys, but not sure. That leaves the water pump and idler drive belt which has more like 140-150 degrees purchase on the pulleys. I believe this is the problem belt - but not 100% sure.

What to do? Do I need to sand blast the pulley surfaces? None of them appear real slick but kind of hard to always tell where the belt is riding in the groove. The water pump idler pulley used to sit a little crooked but I worked on it some years ago and got it straight - I can’t even remember what I did to it I’ve been fighting this so long. Anybody got any ideas on this?

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I can tell you what we did at the dealership back in the 70's when they were new, take a bar of ivory soap and hold against the side of the belts with it running and most of the time the noise will go away and stay away.

 

[AR67GTX]

I can tell you what we did at the dealership back in the 70's when they were new, take a bar of ivory soap and hold against the side of the belts with it running and most of the time the noise will go away and stay away.

I’ll remember that for the next time. That’s hard belt to get to though, right next to and fully behind the fan. Did you ever just take a belt off and rub it down on a work bench with the soap?

 

[Geoff 2]

Cogged/notched belts have less rubber in them. So they stretch more. Try & find some plain old fashioned belts..

 

[68_661charger]

Many years ago I had access to free powder coating and everything went to the powder coaters including the crank and water pump pulleys. Man did they squeek.....