Belt/pulley squeal

[73pony]

Ok so looking for suggestions. I get a belt squeal when you increase the engine RPMs rapidly. Does not happen under normal acceleration or even if I really get on it once the RPMs are already over about 2000. Tried to pin point a pulley while under the hood but could not. All belts are new and tension is good on all. Any ideas would be helpful. I feel like I am missing something simple.

 

[nailpounder]

try belt lube in a spray can @ the auto store

 

[Bentworker]

How is your alternator and voltage regulator? If the regulator is bad sometimes it will go to full output all the time and draw too much horsepower for a single v belt. Same thing can happen with a high current output aftermarket alternator.

Also all belts are not the same, some are poor when they are brand new.

I battled a squealing belt on my 83' GMC pickup. I tried all sorts of different brands, Gates, Dayco, and a couple cheap ones. Finally settled on a magic unicorn belt made by Acdelco that was specific for the application. It was taller in profile than most and seemed to have much more reinforcement. The GMC is probably the worst case application for a single v belt since it is diesel with dual batteries and a single large alternator.

Try some different belts. I had pretty good luck with the Dayco top cog belts being quiet, but the GMC still killed them because the belt profile was so short that there just wasn't enough contact with the pulley for a 100 amp alternator.

Also, pulleys can wear out and sometimes remanufactued parts have incorrect pulleys on them. Also a crankshaft pulley that is out of round can also cause issues.

 

[jb73Mach]

Got AC? How old is the compressor?

 

[piper62j]

The general rule of thumb for these older car drive belts, total deflection from the center line at the widest point, should be a total of 1/2". I don't use a belt tensioner gauge (mainly because I don't have one), but they are available.. Hopefully, they come with the correct information for your application. Over tightening a belt can put a strain on the alternator, ac compressor clutch and power steering shaft bearings..

Pulleys should last the life of the car unless damaged somewhere along their use..

 

[Don C]

I would also check pulley alignment.

 

[73pony]

All belts were replaced with the Gates Green Strip (HD) belt and seem to very nice and heavy compared to the cheaper alternatives. I had this issue prior to the new belts (thought it would take care of the issue as the old belts were pretty worn. Deflection is right about 1/2" on all. I think I will start by isolating each one and see which on squeals while hooked up. My thought is possibly the alt belt as while hard to determine where the sound is coming from it seems to be slightly louder on that side.

 

[Bill73Ragtop]

The good news is your carb is tuned nicely and ramps up really fast when you give it the pedal.

Obviously, the belts are not keeping up so there's a bit of slippage until they catch up. As you stated, normal cruising and acceleration is not a problem and if you are already up over 2,000rpm there is no slippage. I have the same issue with my 351C A/C belt, but for the rare occasion when I put the pedal to the metal, it doesn't seem worth it to over tighten the tension and create more issues by stressing the shaft bearings as Piper62j noted. You could try to rough up of the inner groove surfaces of the pulleys using scuff pads (NOT while the engine is running!) which may help for awhile.

 

[73pony]

The good news is your carb is tuned nicely and ramps up really fast when you give it the pedal.

Obviously, the belts are not keeping up so there's a bit of slippage until they catch up. As you stated, normal cruising and acceleration is not a problem and if you are already up over 2,000rpm there is no slippage. I have the same issue with my 351C A/C belt, but for the rare occasion when I put the pedal to the metal, it doesn't seem worth it to over tighten the tension and create more issues by stressing the shaft bearings as Piper62j noted. You could try to rough up of the inner groove surfaces of the pulleys using scuff pads (NOT while the engine is running!) which may help for awile.

HA! Great minds think alike! Pulled the belts one by one last night and tested. The alternator belt was slipping on the crank pulley (or at least that is what I determined). I cleaned up the insides of all the pulleys to remove any oil or grease and grime then scuffed them with a medium scotch brite pad. By the time I was done it was too late to be revving the engine, as my neighbors already don't like me working on the car. Decided it was to be 84 and sunny today so I took her to work and NO SQUEAL!!!!!! YEAH! I did double check all of the belt deflection after reinstallation and all are set to right at 1/2". And yes for an old Motorcraft 2 bbl carb it is pretty snappy.

 

[73pony]

Update. The squeal came back. Grrrr. Had a friend over and we ran some tests. Bentworker was right. The voltage regulator was going to full output immediatly. Switched it out with a electronic regulator and fixed. Charging right and no squeal! Sweet. Thanks for all the help and suggestions on this one.

 

[Bentworker]

Update. The squeal came back. Grrrr. Had a friend over and we ran some tests. Bentworker was right. The voltage regulator was going to full output immediatly. Switched it out with a electronic regulator and fixed. Charging right and no squeal! Sweet. Thanks for all the help and suggestions on this one.

Glad you got it fixed!

 

[73pony]

Update. The squeal came back. Grrrr. Had a friend over and we ran some tests. Bentworker was right. The voltage regulator was going to full output immediatly. Switched it out with a electronic regulator and fixed. Charging right and no squeal! Sweet. Thanks for all the help and suggestions on this one.

Glad you got it fixed!

Me too. Very embarrassing and annoying. Thanks for the suggestion of where to look. Prob would have been a lot of searching before I thought of that.