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briandors

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1995 Cutlass Supreme convertible.

 

Back in September I found that my rear passenger's side brake caliper had a tear in the piston boot, so I decided to replace it. I torqued everything according to the service manual, and bled the caliper. Everything worked great, no problems. A few hundred miles later, while braking I began hearing this crunch-like sound that was apparently happening once per wheel rotation. It only happened while driving slowly and applying the brakes maybe around 30% of full pressure with my foot.

 

I figured I had gotten a bad caliper, so I replaced it. That one lasted a few months, and it started acting the same. I assumed I had gotten a second bad one, since this one lasted a lot longer. So about two months ago I threw a 3rd one on.

 

Well the noise came back today. This is driving me so crazy. :willynilly:

 

If I brake very lightly, or hard, there is no noise. You also don't hear anything until you're down to around 20mph or less. The parking brake seems to hold the car well, I think it's adjusted ok.

 

Any ideas?

 

Brian

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Pads are Morse Ceramic and newer. I've used this brand and type on the other side of the car, no issues, and on other cars with no issues. I have thought about the rotor. Some kind of deformity in one spot on the rotor would make sense, explain the crunch-crunch-crunch-crunch repetitive sound... that slows down as you slow down.

 

I also notice that it's worse after the brakes have been used a few times and have warmed up.

 

Maybe I'll throw a new rotor on.

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yeah I'd spring for new rotors, or at least get the current ones mic'd and turned. How do the pads look when you're taking the calipers off....uneven? grooved? Are the shims and anti-rattle clips sitting in place?

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Clips are in place, pads are wearing very evenly, nothing unusual. No grooves or chunks missing or anything.

 

Every time i replaced the caliper, I liberally greased up the slides. So they've been freshly greased, every few months on average. I'm using Permatex's Synthetic Disc Brake Slide Grease, it's specially made for this purpose. I've used it in other applications and not had problems.

 

Doesn't make the noise when the car is sitting still. The noise doesn't sound like its the sliders themselves grinding as they slide around. It's more of a rubbing/grinding/grabbing-crunch.

 

If I had the noise before the first caliper replacement, I would have definitely suspected the rotor. The weird thing is it only started after the new caliper, but then, only after its been on there for a while.

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As Brian said, I'd try new rotors.

 

That, or call up a few repair garages around town. Tell them whats going on, and ask them what they think. They probably see and hear all sorts of wierd problems all the time.

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Pads are Morse Ceramic and newer. I've used this brand and type on the other side of the car, no issues, and on other cars with no issues. I have thought about the rotor. Some kind of deformity in one spot on the rotor would make sense, explain the crunch-crunch-crunch-crunch repetitive sound... that slows down as you slow down.

 

I also notice that it's worse after the brakes have been used a few times and have warmed up.

 

Maybe I'll throw a new rotor on.

 

To ask you essential questions:

 

Are you using stock rotors? if not what?

Are you using resurfaced rotors?

Are your rotors warped?

 

One thing I asked about when I joined here years ago was about using ceramic pads. I was told that it was a bad idea to use them with stock rotors as it actually led to decreased brake performance (as if our breaks needed that :roll:). If you are using resurfaced rotors, they may be too thin and past their useful life span.

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Now back to me... :wink:

 

Wierd...I just started having the same problem recently. I was going to post about it, but I'll leach off the info here if you don't mind. :wink:

 

I on the other hand am using OEM or higher Bendix rotors with Raybestos pads (can't remember if they're metallic or semi-metallic). I had great brakes until after the winter this year, and I had to replace a leaking right front brake line. Ever since, my breaks haven't been the same. Yes, it was done right because the dealer did it on a day we had a snow storm. :mad:

 

*EDIT*: Forgot, my rotors and pads are just over a year old (done in Feb '05). They have about 20-25k miles on them, and worked GREAT until that brake line went this winter. Yes, brakes were bled both by the dealer and again by me to try and improve performance.

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If I had the noise before the first caliper replacement, I would have definitely suspected the rotor. The weird thing is it only started after the new caliper, but then, only after its been on there for a while.

 

I'm betting the old caliper wasn't applying at full pressure cause of the tear in the boot. That would be why you didn't hear the noise then. Just a guess.

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Clips are in place, pads are wearing very evenly, nothing unusual. No grooves or chunks missing or anything.

 

Every time i replaced the caliper, I liberally greased up the slides. So they've been freshly greased, every few months on average. I'm using Permatex's Synthetic Disc Brake Slide Grease, it's specially made for this purpose. I've used it in other applications and not had problems.

 

Doesn't make the noise when the car is sitting still. The noise doesn't sound like its the sliders themselves grinding as they slide around. It's more of a rubbing/grinding/grabbing-crunch.

 

If I had the noise before the first caliper replacement, I would have definitely suspected the rotor. The weird thing is it only started after the new caliper, but then, only after its been on there for a while.

 

well with the old caliper, if one or both sliders were stuck a little or siezed, then the pads may not have been touching the rotor at all, or just hitting it partially, causing the rotor to rust/pit in an area thus causing the noise you hear.

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There's no visible rust or pitting, no major pulsation. I did have them turned on the lathe when I put the first new caliper on.

 

Maybe there is a problem with the metal being stickier in one section or something. Also yesterday was much cooler than the day before, so I didn't hear it once. I guess when it comes back I'll check that the caliper is still able to slide around, and then replace the rotor.

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