I have a 94 90S and have a brake groan comimg out of the right front when I am backing. The noise sometimes happens going forward but not often. When this happens you can feel it in the pedal and it seems like there may be air in the system. Bled the brakes but still have the problem. I did not bleed the master as I am not sure on how to do this. This may be the problem. Any ideas and does anyone know how to bleed the master. Thanks. Kevin

 

You may have uneven pad wear. I have found "deglazing" them helps solve this or a piston needs lub.

 

The easiest way to bleed the brakes is the "gravity bleed" method, it's just a bit slow.

Make sure you have a deep-drive socket or box end wrench to open the bleeder screw located behind the caliper. Attach a piece of 1/4" vacume hose to it. Make sure it is long enough to reach to the bottle or coffee can that you will have on the ground to catch the run off.

Remove the cap from the Master Cylinder and leave it off. pour in some NEW brake fluid. If you don't see fluid coming out of the bleeder screw, press the brake pedal and hold it for a few seconds, then check again. Brake fluid should be flowing slowly out.

If you still have no fluid coming out, and the bleeder screw is loose, you probably have a leaky caliper.

The other method requires two people, one to push the brake pedal, and one to work the bleeder screws.

Loosen the bleeder screw with a box-end wrench. the other person pushes the brake pedal down and holds until fluid stops flowing. Tighten the screw with the peddal still down. let up off the brake after that and repeat untill no air bubbles are found. Don't forget to add brake fluid as you go, or you will be repeating the process for a very long time.

The goal of brake bleeding is to remove air from the brake lines. This is done because air compresses quite well, and brake fluid does not. Air in the brake lines will cause uneven braking, usually evidenced by a pull to one side when slowing or stopping. This is not the same as uneven pad wear, whereby the inner or outer pad wears more than the other.

 

In addition, I was told that there is a proper sequence of the "bleeders." (check manual per Audi)

 

I think you need to closely look at the caliper making the noise. Are the sliders adequately lubricated? is the caliper not releasing when you take your foot off the brake pedal? Try jacking up that wheel and with an assistant on the pedal, see what you can discover
I would look to a local problem on the noisy wheel, not a central problem like air in system. Unless you just had a brake job, how would the air get in, anyway?

 

The caliper is not sticking and the wheel turns freely. The noise started after I had my springs and shocks done. The shop that did the installation is not a dealer but a tire shop. The did not tear down the brakes to change the parts so I am at a loss. The car has abs and when it makes this noise you can sort of feel it in the pedal. It is really strange. I thought that bleeding the sytem may help but it did not. If anyone knows how to bleed the master as this was not done maybe it is the problem. Thanks for any help.

 

Take a CAREFUL look at the pads and rotors, they can tell you alot. Is it coming from one side? Front/back? how are the rotors? is there a thick lip at the top (from excessive wear?) How do the pads look. Let me know.