C4 brake noise??

[dmd]

Just did a major brake job on my '96 LT4 convertible. I'd had some small noise coming from the front that I could never figure out, front pads were worn and never stopped the car well anyway, it pulled to the right on braking, and a warped rotor or two was causing pedal pulsing.

So my plan was to replace the front pads and turn all four rotors. I ordered the professional grade Raybestos OEM replacement pads and took the rotors to CSK for turning due to their being pretty badly scored as well as having pad imprints like what is described in Carroll Smith's StopTech article on the rears, which I've read from beginning to end at least three times. The lathe operator told me there was plenty of thickness left, and he only had to take off about a thousandth on each one - but two of them were indeed warped. I think it was both fronts. While I waited for him to finish, I looked over the pad/rotor service section of the Haynes manual and memorized torque specifications and example photos.

When I went to put it all back together, I noticed some strange things. First, I saw why the front rotors have different part numbers for left/right - the center vanes, just as I thought, were angled directionally. And they were angled to take advantage of movement only in reverse.

I also noticed that the calipers were opening backwards, with the pull pin on the bottom. This meant the caliper frames were installed on the wrong sides of the car too.

This also meant that the pads had to be installed backwards, with the squealer tab on the outboard side instead of the inboard side where it belongs.

Thrilled at having discovered professional incompetence and righting the wrongs, I painstakingly reversed everything and put it on the way it was meant to be by its maker. After proper retorquing of all the bolts and reinstalling the wheels with proper lugnut torque, I pumped the pedal back to firmness and set off for testing.

All went well and the pads seated back in nicely. I've been driving the car every day for the last four days, and it's been getting better each day - and all the previous problems are solved, except one.

I've still got some noises. At slow speeds I hear a constant chirp-chirp-chirp, which stops if I put any pressure on the brake pedal. Seems to be coming from the front, but I can't be sure. I also think I'm hearing strange woop-woop-woop noises from the rear at slow speeds.

So my question is this: if I put the clips on the front pads like I was supposed to and reassembled it all like it was supposed to be, is there something I missed with some silicone grease or a shim somewhere? What could cause this with brand-new pads?

Thanks,
Dave D

 

[oldvet]

Just did a major brake job on my '96 LT4 convertible. I'd had some small noise coming from the front that I could never figure out, front pads were worn and never stopped the car well anyway, it pulled to the right on braking, and a warped rotor or two was causing pedal pulsing.

So my plan was to replace the front pads and turn all four rotors. I ordered the professional grade Raybestos OEM replacement pads and took the rotors to CSK for turning due to their being pretty badly scored as well as having pad imprints like what is described in Carroll Smith's StopTech article on the rears, which I've read from beginning to end at least three times. The lathe operator told me there was plenty of thickness left, and he only had to take off about a thousandth on each one - but two of them were indeed warped. I think it was both fronts. While I waited for him to finish, I looked over the pad/rotor service section of the Haynes manual and memorized torque specifications and example photos.

When I went to put it all back together, I noticed some strange things. First, I saw why the front rotors have different part numbers for left/right - the center vanes, just as I thought, were angled directionally. And they were angled to take advantage of movement only in reverse.

I also noticed that the calipers were opening backwards, with the pull pin on the bottom. This meant the caliper frames were installed on the wrong sides of the car too.

This also meant that the pads had to be installed backwards, with the squealer tab on the outboard side instead of the inboard side where it belongs.

Thrilled at having discovered professional incompetence and righting the wrongs, I painstakingly reversed everything and put it on the way it was meant to be by its maker. After proper retorquing of all the bolts and reinstalling the wheels with proper lugnut torque, I pumped the pedal back to firmness and set off for testing.

All went well and the pads seated back in nicely. I've been driving the car every day for the last four days, and it's been getting better each day - and all the previous problems are solved, except one.

I've still got some noises. At slow speeds I hear a constant chirp-chirp-chirp, which stops if I put any pressure on the brake pedal. Seems to be coming from the front, but I can't be sure. I also think I'm hearing strange woop-woop-woop noises from the rear at slow speeds.

So my question is this: if I put the clips on the front pads like I was supposed to and reassembled it all like it was supposed to be, is there something I missed with some silicone grease or a shim somewhere? What could cause this with brand-new pads?

Thanks,
Dave D

Cain't help with the rear brakes, but with the fron brakes, try doing an emergency stop about five times and see if this stops the noise. Its all to do with the material they are putting in the pads.

 

[dmd]

Five times in rapid sequence, or five times with plenty of cool-down in between?

 

[oldvet]

Get it up to about forty and stop it as fast as you can without locking the brakes. Then get it back up to forty and repeat the procedure. The noise might stop after the first time. But usually four or five times is required..

 

[dmd]

Tried it about 5 times, but the noise came back as soon as the brakes cooled down.

 

[oldvet]

Tried it about 5 times, but the noise came back as soon as the brakes cooled down.

What I told you to do is what the dealer told me. So, do you believe the noise is isolated to the pads, now that you tried this procedure? What the dealer told me was that the new OEM pads have alot of ceramics in them, and they have to be broken in. And the only way is the way that I told you. My brakes are still making noise every now then, but the frequency is alot less. Sometime I can go a week
with no noise and then it may do it twice in a week.

Perhaps someone else may like to get in to this.