Brake Squeal / Moan

iamtheari · 04-13-2014, 03:51 PM

On my 1990 C4, I put on Raybestos ST-43 pads and had my rotors machined. I expected a little bit of noise compared to the stock pads, but not quite this much. When stopping at low speeds, at least two of the brakes squeal at a high pitch. Then there is a final big squeak as I come to a stop. From a start, I think just one of them makes a lower-pitched moaning sound at some point on the first revolution of the wheels. And then there is a recurring small squeak (not loud) that sounds like it is once per revolution of the wheels.

I have the stock calipers, new stainless steel braided brake lines, newly flushed and twice-bled fluid, etc. I installed the pads as they came from the manufacturer, which did not include any kind of a vibration dampening plate, grease, or other material.

Happy to hear all ideas of what I did wrong or what I can do to correct this, as the noise is bad enough to turn heads at stop lights and not in the way I prefer. The noise when starting from a stop in particular is a nuisance. Thanks!

Busta Rib · 04-13-2014, 04:09 PM

Make sure you installed the spider-shaped OE noise dampers that help minimize squealing. Also, I advise against anything but OE pads. My brakes were squealing and I just swapped to stock pads that were softer than the sport-performance pads and no more squealing.

iamtheari · 04-13-2014, 04:17 PM

The spider springs were all securely in place when I buttoned up. I noticed now on the way to supper (after my 180 mile drive here and a rest) that the moaning continues longer and the ABS warning light saw fit to come on for me when that started. Very frustrating especially away from home when I was planning to get it teaches while here this week ahead of the first track event near me.

iamtheari · 04-14-2014, 09:19 PM

Correction to above iPhone autocorrection: Teched. And what's the chance that this is a brake caliper issue? Maybe one or more calipers aren't operating smoothly and that's my issue? I have decided to cancel the technical inspection and live without the spring DE event. I will fix the problem instead. Hoping for some diagnostic tips to help me get there without reinventing too many wheels, though. Thanks all.

porterdog · 04-15-2014, 06:43 AM

Have you done a burn/bed in?

iamtheari · 04-15-2014, 07:16 AM

Yes. That seemed to go smoothly. I did a series of stops from 75 to 25 under progressively harder braking and then a cool down drive.

iamtheari · 04-15-2014, 03:57 PM

I am unfortunately far from my jack so I can't look at anything closely until this weekend, but I did note a slight metallic clunk sound one time. As I think about it, this is very similar to the sound the brake pads make when you first install them into the caliper, as they slide home. So it's probably something to do with the retention springs, is my current thinking. Further input welcome as I eagerly await a chance to look at it. Thanks again.

iamtheari · 05-13-2014, 08:33 AM

I haven't had a chance to spend much time with the car lately. I did jack up one corner at a time this weekend and rotate the wheel by hand. There was some intermittent resistance that seems normal from past experience. No squeals or moans.

I read a bit today to try to find potential sources of the problem I am having. It appears that the most likely causes are:

1. Brake pads and spring not quite perfectly in place. Unlikely because I was very careful about the springs going in correctly, but quick to check when taking off a wheel.

2. Brake caliper pistons sticking and not releasing the pad fully. This appears unlikely in general but, if it's the case, a caliper rebuild is in order.

3. Brake pads sticking due to corrosion in or behind the metal spring plates on the leading and trailing sides of the brake pad area in the caliper. This sounds likely to me because some pads have been very tight to go in and out of the calipers.

Does anyone have a DIY process, ideally on-car, to deal with the spring plate issues? I have heard that the screws are very difficult to remove. Other than that, what process should I follow? Remove the plates, gently brush out corrosion, and put them back on? Or something more complicated/involved?

Thanks.

pantera · 01:20 PM

Have you used this type of pad before? Being you had the rotors freshly cut and your using brand new race pads your essentially bedding in both at the same time. Its possible you might have a slight glaze over the rotors and they might need further bedding in....getting some more pad material onto the disc.

Dan

PS X post this on the Track forum to get some more feed back.

iamtheari · 05-13-2014, 01:20 PM

I haven't used this type of pads before, but there is no way this is normal. Even when coasting at slow speed without having applied the brakes, it does this one-squeal-per-wheel-revolution thing. It's beyond loud. It occasionally turns on the ABS warning light, which stays on until the ignition is shut off and it resets. There is something wrong with the brake system.

crg53 · 05-13-2014, 04:59 PM

You will not be able to fix the spring plates without removing the calipers. What you can do is custom fit the brake pads so they slide into places by filing a small amount off the metal backing plate on the pad itself. If the pads are tight, they will squeal.

iamtheari · 05-13-2014, 08:33 PM

Filing a small amount off the pad backing plates to get the right fit for this set of pads and then rebuilding the calipers when the pads wear out is the way I'm leaning right now. So I can plan ahead, does anyone have recommendations for caliper rebuilders?

I know it's not a difficult job, but the parts are expensive to buy and if it's only a marginally higher price to get them done professionally, I prefer that route. I did the same thing with my steering rack--realized that it was not beyond my ability but beyond my free time and patience and that I could get it rebuilt professionally for a fair price and not have to worry about it at speed.

Nine9six · Nine9six's Garage

I dont know about 964 application, but the 993's are very picky about anything other than Porsche or Textar OE pads.

The anti-squeel spiders make little difference when used with foreign pads.

HTH

iamtheari · 05-16-2014, 07:56 PM

I've never bothered with the anti-squeal spiders. A little noise is expected from a trackable car.

iamtheari · 08-05-2014, 08:01 AM

I ended up just having the calipers rebuilt by Hayworth Racing Brakes. The pads slid right in and all is well, although the Raybestos ST-43 pads are definitely squealers. That's fine. The big moaning sound even at low speeds when I hadn't been braking is gone. A little chirpy as I drive but nothing bad, squeaky sometimes when I stop and they're cold but that's a track car for you, etc.

I can strongly recommend Hayworth for rebuilding calipers. They did a great job, it cost less than it would have to do a less thorough job myself, and their customer service was really good. Plan ahead since they're busy, but rest assured you'll have good calipers when they come back to you.

iamtheari · 08-05-2014, 02:10 PM

Well, I spoke too soon on the noises. When turning, there is something else going on. A bystander whose office is beneath mine said it sounded like my rear driver side brake 'shoe' is dragging, which could well mean that I have a wheel bearing or other issue. I don't recall anything being loose or wobbly when I put the brake rotors back on the car this spring. Does anyone have tips on what I'm looking for to diagnose and resolve the issue? Thanks again.

RedCoupe · 08-05-2014, 05:05 PM

Have you jacked up the rear to spin your LR wheel? Maybe part of your noise could be something as simple as a hanging up e-brake.

iamtheari · 08-05-2014, 06:30 PM

I am inclined to just remove the emergency brake to eliminate it as a cause. It has never worked well and my attempts to adjust it have all led to frustration. Including the major attempt that coincided with the onset of these symptoms (when I could spray it down with PB blaster when the rotors were off).

bazar01 · bazar01's Garage

The e-brake is a small drum brake inside the hat on the rotor. If the rear bearing is good, it could be a loose e-brake shoe to cause it to rattle or too tight to grab when it heats up.
It's really very easy to adjust the e-brake. Just make sure you get 3-4 clicks on the e-brake handle to engage. Just one click will drag and grab when it heats up.
Good luck.

sand_man · 08-06-2014, 07:07 AM

Quote:

Originally Posted by Nine9six

I dont know about 964 application, but the 993's are very picky about anything other than Porsche or Textar OE pads.

The anti-squeel spiders make little difference when used with foreign pads.

HTH

This is what my research revealed, as well. Not sure if the same applies to the 964. Also, I left out the dampening "spiders" when I last did a pad change. They made little difference if any. Sealed them up in a baggie for the next guy (if there is one).