I'm running into some odd brake noise. Sometimes, when braking gradually downhill, I get a strange moaning noise from the rear brakes, but generally only around 10-30mph. It also happens occasionally when backing up. It doesn't sound like a normal brake groan, or squeak. It sounds more like the sound when you blow across an empty glass bottle, and almost doesn't feel like it is coming from the brakes.

The car is a 2005 SE, the brakes are all less than 15k old, and checked out okay the last time they were measured, about 5k ago. The rear brakes have squeaked a little from the day they were put on, were checked, and nothing was found wrong.

Any ideas?

Mine do that too. There are plenty of tricks to keep brakes quiet. Everything can be mechanically sound and you can still get noise. Sometimes there are special pads to install behind the brake pads, or some goo to put on the back of the brake pad.

Usually the noise is just annoying and not a real safety issue. You say the brakes are fairly new and have been inspected so this is probably the case here.

I am putting up with mine until they need to be replaced anyway, then I will spend the effort to get them quiet.

Hawkjet,

Thanks for the advice. I didn't figure it was a safety issue, but it sure is embarassing.

so whats the fix here ?
my 92 does it really badly

the brakes work fine

really noisy hum/moan grab noise

especially when after sitting in high humidity and when cold

really bad

how do you fix this

what is the exact cause

is it the brake pad material face contact to rotor face ?

or the backside of the pads to the caliper and piston contact ?

and how/why ?


if its the pads doing it then what pads do you get that wont do this ?


thanks

GM issued a TSB for that issue for the 2000 and 2001 model years, that should have been already applied to yours.
There are several good brands of pads that could lessen the problem. They may have shims attached to the back, or have a special coating. Some will bevel the edges of the pads, and others may have a slit down the center to lessen the vibrations. If you want to try some new pads, go to a good auto parts store that has a knowledgeable person at the counter, or you could try some things on your own, with your current pads.

Buy some disc brake quiet, and apply it to the back of the pads, after cleaning them well. Also clean up the caliper piston. Clean up the metal pad clips well, and apply a touch of brake lube to them, as well as lubing the caliper bolts and pins well. You could also try filing down the side edges of the pads a touch, with a file.

A '92 has drum brakes in the rear, so is a totally different animal. Your best bet is to pull the drums, and inspect the brakes. Check the brake wheel cylinder for leakage, and look for any broken springs. If the cylinder is leaking, replace it, clean up the drum well, and replace the shoes. Also, make sure the brakes are adjusted properly. If you need additional help, that would be better posted in the 92-99 section.