Noisy rear discs

[iTurbo]

The rear disc brakes on my Omni GLH Turbo are noisy, but only when it's wet outside. They make a squeaking/groaning noise when it's wet outside and only for the first few minutes of driving. After they dry out, they stop making the noise. The noise is really loud when going in reverse and I notice it most when backing out of a parking space when it's wet outside. I don't even have to be pressing on the brakes to make the noise but if I do apply the brakes the groaning noise gets a lot louder.

The rear brakes are 11" rear vented discs from a '91 Lebaron GTC. Pads are the 911 brake pads from FWDP. Calipers are Raybestos remaned units with stainless steel pistons. I'm also using DOT 4 fluid. The rotors are fairly new as well and I haven't seen any unusual wear.

I've taken them apart and am sure they are put together right and the pads are clipped in correctly and everything is tight. Any ideas?

[supercrackerbox]

Did you grease everything properly? Go to the parts store of your choice and look for caliper grease or brake quiet grease, same stuff really. Pull the pins out of the caliper, make sure they are clean, and lube them up nice and good, also smear it on the mounting bracket where the caliper slides back and forth. Finally put a good smear across the back of each pad. This will basically absorb the harmonics of the pad riding on the disc. Also, if you didn't have the rotors turned before putting new pads on, do that as well. Otherwise the pad usually won't seat properly to the rotor and will sqeal like hell.

[iTurbo]

I'll have to check the lube again. When I first installed them I used some brake grease from Checker that comes in the little green packet. The reman calipers came assembled with new boots and pins with grease already in them. I applied the lube to the rails on the back plate where the pads ride on them, and to the backside of the pad where it contacts the piston. I also lubed the clips that secure the pad to the calipers/piston so they could move freely.

Also, this morning it was nice and dry outside, but the rear discs were groaning very loudly when I backed out of my parking space and applied the brakes. The noise disappears after using the brakes once or twice. Could this be related to brake dust buildup?

[86Shelby]

First, aren't the 911 pads a higher temp pad compound? That in itself can cause noise and poor braking when the pads are cold. Once they warm up they should be just dandy.

Any chance that your rotors are getting wet from condensation or rain? I see this problem on a regular basis from customers that wash thier cars very often. A small amount of surface rust builds up on the outer surface of the rotor, which then is rubbed off by the pad during the first few stops. The problem is that the rust gets imbedded in the pad. That causes noise. It usually starts off being intermittent, only during the first few stops. Then it progresses to the noise depending on how hard you are braking. Finally it makes the noise all the time, regardless of temp, humidity, braking pressure, etc. This also happens to customers cars that sit for a few days and then driven, then sit and so on.

The best fix that I have found is to turn both rotors, or go over them carefully with some emery cloth. Get a nice non-directional pattern on the surface the pads contact. Resurface the pads with emery cloth to remove all the rust buildup. You can usually see a few brown or orange streaks on the surface of the pad when this occurs. Once the pads are resurfaced I'll treat them with BG anti-squeal coating on the friction surface and a stickier Car Quest brake quiet spray on the rear. Lube up all the sliders, pins, brackets etc with caliper lube. Reassemble and do several meduim to hard braking stops. Hard enough to make something fall off the seats.

[iTurbo]

Thanks guys. I'll pull the brakes apart again check everything out. I'll probably try some different brake pads while I'm at it. It seems they are always VERY noisy the first couple times I use them every day, than it goes away. If it's wet out it's a lot worse and will even make the noise when the car is rolling backwards with no brakes applied. It doesn't make the noise rolling forward however.

If it's wet out, it's so bad I can push up and down on the rear of the car (parked) and the brakes will groan with slight movement of the rear wheel. It's like the caliper isn't fully disengaging but the brakes don't seem to be sticking any time I drive it. It think there must be a lot of brake dust or rust buildup between the rotor and pad.

[iTurbo]

Also, the rear brakes seem very grabby, especially when it's making the noise. Under extreme braking, the rear discs lock up prematurely. This can make for a pretty hairy ride, with the rear end losing control and fishtailing. I've wondered if it's related to the problem I'm having with rear brakes or just that the 11" rear disc setup is too much for an L-body.

[Force Fed Mopar]

I have the same thing on my GLHS, except it does it when they get warm. I have the solid non-vented rear discs of my 89 Lebaron on it, w/ cheap WearEver pads from Advance. 99% of the time they are perfectly fine, but if I stop hard twice and put some heat into them, they grab real good but make a horrible groaning noise under light brake pressure, sounds like something binding up.

I didn't have the rotors turns when I installed them, though, and they had a good bit of rust on them from sitting around. I was kinda thinking the rust may have gotten embedded in the pads and makes the noise when they get hot? Doesn't make the noise under hard braking even when hot, and stops like a mofo, hard enough to throw the oil pressure light on.

[afsautoworx]

Get some organic pads for the rear. Wont put you thru the windshield when u stop after its rained.