Weird braking problem, noise. Help!

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DanteGTZ
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Weird braking problem, noise. Help!

Postby DanteGTZ » Sun Nov 20, 2016 6:54 pm

I recently did the rear disc swap and now have a noise that I can't seem to track down. First, let me give you some background. This is on my '93 GTZ (w/ABS). Front brakes are the 95+ J-body Wilwood 4 piston setup and have worked fine for almost a year now. No complaints.

I installed my Neon rear disc setup and although performance seems fine, after doing a few normal stops a noise will begin to develop that is driving me crazy. The sound happens when the pedal is depressed. It is more prominent at very low speeds, almost stopped. The noise is NOT a grinding sound and NOT a typical brake pad squeal. The best way sound I can compare it to is the sound of a school bus or dump truck braking. It sounds very much like some kind harmonic going through metal instead of a normal squeak or squealing pad. The sound is so loud that I can feel it through the chassis of the car. The only way to quiet it down (as I come to a stop) is to push harder on the pedal. The noise goes away quickly after I start moving again. Occasionally I can hear it slightly as I drive down the road, just after a previous stop. After stopping, I have noticed that the wheel on the caliper in question is noticeably warmer than the other 3, as if the caliper is sticking.

I've taken the brakes apart and checked everything. Everything looks normal, no signs of wear or anything obvious. I've greased the pins as well, although they show no signs of wear at all.

I've put everything back together MINUS the e-brake setup (just in case that was causing some issue).

I have bled the system repeatedly. Starting at the master/ABS module and working my way back. A couple things I've noticed:

(1) The master/ABS module has to bleed ports on it, which I've bled. I discovered these bleed nipples originally because I was unable to properly bleed the driver's side REAR caliper and the passenger side FRONT caliper (this is AFTER the rear disc install). Tracing the lines back, I found the bleed valves on the ABS module. After bleeding a ton of air out of one of the ports I was then able to bleed the above-mentioned calipers. It appears that the drivers front and passenger rear are tied together and the drivers rear and passenger front are also tied together, or at least correlated within the ABS/master cyl.

(2) After making that first connection, I became more acutely aware of the sound and where it appeared to come from. Interestingly enough, I noticed the sound (although quieter than when the car is rolling) when I bled the rear drivers side caliper. No idea how bleeding a caliper could make that noise, but it did, a few times. Other than that, I'm fairly certain that the front PASSENGER side caliper is also causing this same noise, although less frequently than the driver rear.

Any idea what could be happening? Could I have a bad ABS/master? What else could I be missing?

- Neon rear rotor/caliper/bracket
- Hawks rear pads
- NEW stainless hoses to rear calipers
- All brakes are recently bled and new fluid is at each caliper


1993 Quasar Quad4 GTZ - Project WTF
1993 Garnet Quad4 GTZ - GTZed-Eh? - SOLD
1993 Aqua GT - 3.1 / 5 speed - 82k original miles - SOLD

Previous Berettas: 1990 GT and 1993 Quasar GTZ

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Re: Weird braking problem, noise. Help!

Postby ifixalot » Mon Nov 21, 2016 9:28 am

This is just an idea that came to mind. You say the front and rear that make the noise are tied together.
On my daughters 96, we had an issue of rust on the front brake hose bracket where it is crimped around to grip the hose,
this was squeezing the hose closed which caused her brake caliper to drag and heat up.
If you have rusty front brake hose brackets, it may be causing some pressure to remain in that circuit
and making both the front and rear pads drag slightly????



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Re: Weird braking problem, noise. Help!

Postby 3X00-Modified » Mon Nov 21, 2016 10:45 am

He has aftermarket brakes and aftermarket stainless braided lines... All of those "typical" issues can really be wiped off the table.

The fact that you have this noise spread between the front and the rear's can almost rule out the pads or rotors since they aren't the same setup front to rear... next on the list is once again fluid flow, and or restriction in your system. It's probably time for you to upgrade and replace the master cylinder just to be sure... And you really should anyways since you did the disc rear setup. My car makes a hell of a howl when I apply the brakes lightly when they are stone cold but I know that is pad compound causing that so it doesn't bother me. If I change to a softer HAWK pad the sound goes away.



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Re: Weird braking problem, noise. Help!

Postby 3X00-Modified » Mon Nov 21, 2016 10:47 am

And for reference this is how the ports are split on the master. The assignment you speak of has nothing to do with the ABS... Remember the abs system is basically a pass through when not in operation, it doesn't change anything else about how the system works.

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Re: Weird braking problem, noise. Help!

Postby DanteGTZ » Mon Nov 21, 2016 7:58 pm

3X00-Modified wrote:He has aftermarket brakes and aftermarket stainless braided lines... All of those "typical" issues can really be wiped off the table.

The fact that you have this noise spread between the front and the rear's can almost rule out the pads or rotors since they aren't the same setup front to rear... next on the list is once again fluid flow, and or restriction in your system. It's probably time for you to upgrade and replace the master cylinder just to be sure... And you really should anyways since you did the disc rear setup. My car makes a hell of a howl when I apply the brakes lightly when they are stone cold but I know that is pad compound causing that so it doesn't bother me. If I change to a softer HAWK pad the sound goes away.


I'm still a bit confused as to which master I'd need. I have a '93 Lumina Z34 master that I had been planning on using, but I'm not sure it'll match things all that well. FWIW, my pedal feel isn't all that bad at the moment - It's still pretty firm although I will say it doesn't seem to grip as hard as it did before the rear discs.

Are there rebuild kits for these masters available? I remember taking apart a Camaro master a few years back and it looked pretty basic inside.


1993 Quasar Quad4 GTZ - Project WTF
1993 Garnet Quad4 GTZ - GTZed-Eh? - SOLD
1993 Aqua GT - 3.1 / 5 speed - 82k original miles - SOLD

Previous Berettas: 1990 GT and 1993 Quasar GTZ

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Re: Weird braking problem, noise. Help!

Postby 3X00-Modified » Mon Nov 21, 2016 9:08 pm

You want the master I just took off my car. The ABS Monte/Lumina version.

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DanteGTZ
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Re: Weird braking problem, noise. Help!

Postby DanteGTZ » Mon Nov 21, 2016 9:16 pm

3X00-Modified wrote:You want the master I just took off my car. The ABS Monte/Lumina version.

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Think that'd be the same size as the one I've already got from a '93 Z34?


1993 Quasar Quad4 GTZ - Project WTF
1993 Garnet Quad4 GTZ - GTZed-Eh? - SOLD
1993 Aqua GT - 3.1 / 5 speed - 82k original miles - SOLD

Previous Berettas: 1990 GT and 1993 Quasar GTZ

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Re: Weird braking problem, noise. Help!

Postby 3X00-Modified » Tue Nov 22, 2016 7:52 am

Um, not sure... I'd have to cross my old PN to what you bought to see.




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