Audi Cars 1999-05

Calipers & Wheel Cylinders


When bleeding the brakes, air may be trapped in the brake lines or valves far upstream, as much as 10 feet from the bleeder screw. Therefore, it is very important to have a fast flow of a large volume of brake fluid when bleeding the brakes, to make sure all of the air is expelled from the system.

Proper manual bleeding of the hydraulic brake system will require the use of an assistant unless a suitable self-bleeding tool is available. If using a self-bleeding tool, refer to the manufacturer's directions for tool use and follow the proper bleeding sequence listed in this section.

Avoid spilling brake fluid on the vehicle's paint. It will damage the finish. If a spill does occur, flush it with water immediately.

If the master cylinder reservoir runs dry during the bleeding process, restart from the first fitting.

To bleed the brakes, proceed as follows.

  1. Remove the old brake fluid from the reservoir using a siphon gun or a baster and clean the brake master cylinder reservoir with a clean lint-free cloth. If necessary, remove the reservoir and flush out with brake cleaner.

When bleeding the brakes, the reservoir must be free of all debris and contaminated fluid, otherwise there is a risk that the master cylinder check valve will become contaminated and fail to function properly, requiring replacement of the master cylinder.

  1. Bleed the brake system at each fitting. Do NOT proceed to the next fitting until all air bubbles are removed from the previous fitting. Bleed the brakes, making sure to following this sequence:

    1-Right Rear
    2-Left Rear
    3-Right Front
    4-Left Front

If the vehicle is equipped with a rear pressure regulator, move the regulator lever when bleeding the rear brakes.

  1. Attach a clear plastic hose to the bleeder screw, then place the hose into a clean jar that has enough fresh brake fluid to submerge the end of the hose.
  3. Have an assistant pump the brake pedal ins a smooth, easy fashion, 3-4 times, and hold it down keeping pressure on it, then open the bleeder screw at least 1 / 4 turn. When the bleeder screw opens, the brake pedal may drop further and should be kept pressed down. Have the assistant hold it there until the bleed valve is closed.
  5. Close the bleeder valve and have the assistant slowly release the brake pedal only AFTER the bleeder valve is closed, then check the master cylinder fluid level and top off as necessary.
  7. Repeat the bleeding procedure until all there are no air bubbles, or a minimum of 4 or 5 times at each bleeder screw, then check the pedal for travel and feel. If the pedal travel is excessive, or feels spongy, it's possible enough fluid has not passed through the system to expel all of the trapped air.

Constantly check and top off the master cylinder. Do NOT allow the master cylinder to run dry, otherwise air will re-enter the brake system.

  1. Once completed, pump and check the brake pedal for a firm feel, then, if the pedal pressure is firm, test drive the vehicle to be sure the brakes are operating correctly and that the pedal feel is firm during braking.

If the brake pedal has good pedal pressure after bleeding, but later requires being pumped up to regain pedal pressure, check the system for fluid leaks. If no fluid leaks are present, the master cylinder has most likely failed.