Brake squeal question

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  #1  
Old 05-28-04, 09:06 AM
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Brake squeal question

I have a 94 Oldsmobile Cutlass Supreme Convertible with a 6 cylinder engine.

I changed the front brake pads and rotors about 9 months ago as well as the rear pads, rotors and calipers. Since then, they have never stopped squealing.

The squeal seems to be coming from the front left and when I remove the tire and rotate the rotor by hand, it seems to have a high spot and it squeals everytime it hits it. I think the rotor is warped.

What should I do? Replace the rotors and the pads in front? They are no longer under warranty.

Before you answer you might want to consider some other info on this: I had never done a brake job before this last one. I had considerable difficulty in bleeding the brakes because I almost stripped one of the bleeder screws. I think the one that I had difficulty bleeding is now the one that is squealing.
Then I had to bleed the ABS module too.

Could the squeal be related to air in the system on one brake?

One thing I know for sure is, the squeal happens everytime it hits that supposed "high spot". It only quiets down at high speeds and disappears completely when the brake pedal is applied.

thanks in advance.
 
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  #2  
Old 05-28-04, 02:35 PM
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It's hard to determine just what's going on from here but it sounds like something might be rubbing in that wheel. As a rule the cheaper quality pads are very prone to brake squeel but since your only having the problem in one wheel, I kinda doubt that's what we're dealing with here. As for the warpage in the rotor, that really doesn't have anything to do with squeel and if it's a problem, it will be very noticable when applying the brakes at high speed. You will feel a pulsation and hear a banging when the brakes are applied. Maybe a surging in the brakes at lower speeds. Check to be sure that your backing plate isn't touching the rotor anywhere.
 
  #3  
Old 05-28-04, 02:48 PM
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also suggest checking your wear indicators on the pads as one of them may have gotten bent out of shape which would also cause a noise until the brakes are applied. if its coming from the rear the brake pad may not be laying on the caliper piston flat if i remember correctly there is a notch on the piston and a raised pin on the back of the pad which would cause the pad to be at a slight angle if it was not aligned correctly.
 
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Old 05-28-04, 05:16 PM
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I agree that it is hard to determine the problem. I haven't noticed too much vibration when braking at high speeds but there is some. No surging that I can tell on low-speed braking.

As far as the wear sensors, none is touching.

The backing plate? What would make that rub against the rotor?

I am still thinking warped rotor (but like I said, this is the only brake job I have ever done. So, you are much more likely to be right than me). I think it is warped because when I spin it by hand, it squeaks everytime it hits that certain spot. When I look down between the pad and the rotor, I can see it touch the pad at one spot and that's when I hear the squeak.

How do you recommend I continue with this to try and solve the problem. Replace everything?

thanks
 
  #5  
Old 05-28-04, 05:46 PM
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You very well may have a warped rotor although that is not the root cause of your noise. The backing place by design clears the rotor by less than an eigth of an inch in most places. You can cause it to touch by merely pushing or pulling on it slighty. At this point I would probably remove the pads and start over. Make sure the rotor is seated firmly, have it turned to eliminate any warpage. Makes sure your pads are seated properly and start over. You may have to move to a higher quality pad in the end.
 
  #6  
Old 05-29-04, 07:46 AM
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I'm with Desi - start over. The likely cause of the squeal, in my mind, will be a hard spot in one of the pads. Very common in mettalic pads. To rule out a backing plate, simply run 2 lug nuts down finger tight to seat the rotor on the hub and check the clearance. Also, a high spot in the rotor = warpage, period. On that particular vehicle, I would also determine whether or not you installed "composite" rotors before I had them turned. "Composites" have a very thin sheet-metal center, and they are extremely susceptible to warping. Parts guy should be able to tell you which type you have. If they're composites, throw them away and buy some solid cast ones. Then go with a good quality set of pads, preferably ceramic.
 
  #7  
Old 05-29-04, 09:41 AM
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okay. the first thing i am going to do is investigate the backing plate and see if i can straigten it out if it is rubbing.

if not, i will replace everything.

thanks for the advice
 
  #8  
Old 05-29-04, 02:32 PM
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Originally Posted by robert smith
if not, i will replace everything.
thanks for the advice
Nobody said to replace everything, simply to disassemble and inspect for problems, then repair/replace any problem things found. You never know, the problem may be obvious when you take things apart.
 
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