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Sion · 09-13-2003, 08:27 AM

ok, first off, is there just one belt, or multiple? if one, that eliminates the next step, which is to determine which belt is doing the squealing. this is most easily accomplished using either a spray-on "stop squeal" product or, as mentioned, a bar of soap. just apply the product to each belt in turn until you determine, but the sudden lack of squeal, which is the culprit. once you know which belt it is, then it comes down to determining which of the accessories on that belt (ie power steering, alternator, a/c, smog pump, water pump, etc) on that belt is causing the problem. you see, given the fact that you have had the belt retensioned several times and the problem still recurs, then the answer is one of two things. either:

a) the belt keeps coming loose. if the vehicle has an automatic, spring loaded tensioner (which I doubt, considering what you've said) then I would look at the tensioner. if not, then it is tensioned by the mechanic via one of the accessories being on a pivot (usually the alternator, but not always). in any case, unless your mechanic is incapable of properly tightening a damned bolt, then Id say the belt is not so much coming loose as it is:

b) the bearings in one of the accessory pulleys are going bad. no matter how tight the belt is, IF the bearings in one of the pulleys are beginning to fail (not unlikely given the age of the vehicle) then there will be resistance to the spinning action that the belt provides. hence, the belt will slip and squeal until the pulley reaches the same speed that the belt is travelling. in this situation, it will be necessary to determine which of these pulleys has bad bearings and replace either the pulley (which will come with the bearing) if that is possible, or if not, then the entire accessory part. since you have had the alternator replaced, then we can assume thats not it, since the problem has returned. next two most likely culprits are the airconditioning compressor (if the car has a/c) and the water pump. a/c compressors are notorious causes of belt squeal, because not only do they have bearings which can go bad, but also the pulley itself is part of a clutch mechanism that can fail. here is a quick test to try. start the car and let it run with the a/c off until the belt squeal goes away and the car is warmed up (say 5 mins). now, without touching the gas pedal, put the a/c on. does the belt squeal for a second or 3? if so, you have found your culprit.

if that doesnt pinpoint the bad pulley/bearing, then the only other choice is to remove the belt and hand turn each and every pulley (idler/tensioner pulleys too) that the belt rides on, trying to find the one(s) that dont turn nice and smooth.

absolute worst case scenario: you've tired all of the above and nothing has revealed itself. live with it until such time as the belt WONT STOP squealing no matter what. now you should be able to determine which pulley wont spin freely, as it likely wont spin at all.

btw: find a new mechanic. this one doesnt know his ass from a hole in the ground.

note: contrary to popular belief, if IS possible to overtighten a belt. that is why they have specifications for belt tension (whether V-belt or serpentine, there IS a specification for tension). if you make a belt too tight, it WILL put excess stress on the bearings in ALL the pulleys on that system (even the crank pulley) causing any or all of them to wear out prematurely.

simple rules of thumb for the backyard mechanic who doesnt own a belt tension measuring device:

for V-belts: if you can grab the belt and rotate it 180 degrees, it is TOO LOOSE. you should be able to rotate it about 90 degrees. if not, it is too tight.

for serpentine belts: if you put your thumb on the belt in the middle of a section that is at least 8 inches from pulley to pulley, you should be able to push it down no more than 1/2 inch. if you can push it down more, its too loose. if you cant push it down that much, its too tight.

09-13-2003, 08:27 AM	#7 (permalink)
Sion Dumb all over...a little ugly on the side Location: In the room where the giant fire puffer works, and the torture never stops.	ok, first off, is there just one belt, or multiple? if one, that eliminates the next step, which is to determine which belt is doing the squealing. this is most easily accomplished using either a spray-on "stop squeal" product or, as mentioned, a bar of soap. just apply the product to each belt in turn until you determine, but the sudden lack of squeal, which is the culprit. once you know which belt it is, then it comes down to determining which of the accessories on that belt (ie power steering, alternator, a/c, smog pump, water pump, etc) on that belt is causing the problem. you see, given the fact that you have had the belt retensioned several times and the problem still recurs, then the answer is one of two things. either: a) the belt keeps coming loose. if the vehicle has an automatic, spring loaded tensioner (which I doubt, considering what you've said) then I would look at the tensioner. if not, then it is tensioned by the mechanic via one of the accessories being on a pivot (usually the alternator, but not always). in any case, unless your mechanic is incapable of properly tightening a damned bolt, then Id say the belt is not so much coming loose as it is: b) the bearings in one of the accessory pulleys are going bad. no matter how tight the belt is, IF the bearings in one of the pulleys are beginning to fail (not unlikely given the age of the vehicle) then there will be resistance to the spinning action that the belt provides. hence, the belt will slip and squeal until the pulley reaches the same speed that the belt is travelling. in this situation, it will be necessary to determine which of these pulleys has bad bearings and replace either the pulley (which will come with the bearing) if that is possible, or if not, then the entire accessory part. since you have had the alternator replaced, then we can assume thats not it, since the problem has returned. next two most likely culprits are the airconditioning compressor (if the car has a/c) and the water pump. a/c compressors are notorious causes of belt squeal, because not only do they have bearings which can go bad, but also the pulley itself is part of a clutch mechanism that can fail. here is a quick test to try. start the car and let it run with the a/c off until the belt squeal goes away and the car is warmed up (say 5 mins). now, without touching the gas pedal, put the a/c on. does the belt squeal for a second or 3? if so, you have found your culprit. if that doesnt pinpoint the bad pulley/bearing, then the only other choice is to remove the belt and hand turn each and every pulley (idler/tensioner pulleys too) that the belt rides on, trying to find the one(s) that dont turn nice and smooth. absolute worst case scenario: you've tired all of the above and nothing has revealed itself. live with it until such time as the belt WONT STOP squealing no matter what. now you should be able to determine which pulley wont spin freely, as it likely wont spin at all. btw: find a new mechanic. this one doesnt know his ass from a hole in the ground. note: contrary to popular belief, if IS possible to overtighten a belt. that is why they have specifications for belt tension (whether V-belt or serpentine, there IS a specification for tension). if you make a belt too tight, it WILL put excess stress on the bearings in ALL the pulleys on that system (even the crank pulley) causing any or all of them to wear out prematurely. simple rules of thumb for the backyard mechanic who doesnt own a belt tension measuring device: for V-belts: if you can grab the belt and rotate it 180 degrees, it is TOO LOOSE. you should be able to rotate it about 90 degrees. if not, it is too tight. for serpentine belts: if you put your thumb on the belt in the middle of a section that is at least 8 inches from pulley to pulley, you should be able to push it down no more than 1/2 inch. if you can push it down more, its too loose. if you cant push it down that much, its too tight. __________________ He's the best, of course, of all the worst. Some wrong been done, he done it first. -fz I jus' want ta thank you...falettinme...be mice elf...agin...