2004 Audi A4 Quatto Bleed the Brakes

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The 2004 Audi A4 Quattro comes equipped with four-wheel anti-lock disc brakes to support its all-wheel drive feature. The brake system relies on brake fluid to force the brake pads against the rotors on the wheel hubs during braking. When air is introduced to the brake lines the result is a degraded brake operation in response to depression of the brake pedal. Removing the air is achieved by bleeding the brakes. With the assistance of a helper you can bleed the rear brakes of the Audi in under an hour.

Tools Used[edit]

Lug wrench (or 17 mm socket and breaker bar)
Jack stands
10 mm wrench
Brake bleed kit (including tubing)
Drip pan

Bleed the Brakes[edit]

  • Loosen the lug nuts on the rear wheels with the lug wrench or 17 mm socket and breaker bar.
  • Open the hood of the A4 and remove the master cylinder cap. The master cylinder is the container that holds the brake fluid and is located on the left side of the engine, near the windshield. Place the cap loosely over the container to keep debris from entering the fluid reservoir.
  • Place the lifting jack beneath the frame at the rear of the vehicle and lift the Audi until the tires are clear of the ground by at least two inches. Place jack stands beneath the rear frame to support the car during the brake bleeding.
  • Remove the lug nuts and take the wheels/tires from the wheel bolts.
  • Locate the brake bleed valve on the right-rear brake. The valve is located on the back side of the rear brake caliper. Remove the rubber valve cover from the valve by hand.
  • Place the 10 mm wrench around the valve and then attach the clear tubing from the brake bleed kit. Aim the tubing toward the drip pan below.
  • Instruct your assistant into the cockpit of the Audi and have him begin depressing the brake pedal. The pedal should be pressed three times slowly and held down on the third depression.
  • While the pedal is being held, open the bleed valve by turning the wrench one-quarter turn counterclockwise. The fluid will begin to flow from the valve, through the tube, and into the drip pan. Monitor the flow.
  • Close the valve by turning the wrench clockwise once you notice no bubbles in the stream of brake fluid.
  • Remove the tube and wrench and place them near the left rear brake. Replace the rubber valve cover over the bleed valve.
  • Return to the engine compartment and add brake fluid to the master cylinder reservoir.
  • Remove the left brake bleed valve cover. Place the wrench and tubing on the left-rear brake bleed valve and repeat the process for bleeding the brake. Once finished, remove the tube and wrench from the valve. Replace the rubber cover over the bleed valve.
  • Check the master cylinder and replenish the reservoir as necessary. Place the cap firmly on the container and close the Audi's hood.
  • Replace the rear wheels/tires onto the wheel bolts and screw on the lug nuts by hand.
  • Lift the back end of the A4 with the jack and remove the jack stands. Lower the vehicle to the ground and tighten the lugs with the lug wrench or 17 mm socket and breaker bar.

Tips & Warnings[edit]

  • The order of brakes bled should always be from the farthest brake to the closest brake in relation to the master cylinder. The master cylinder is in the front of the vehicle on the driver's side, so the rear brake on the opposite side should be first, followed by the rear brake on the same side.
  • Use DOT-4 brake fluid to fill the Audi's master cylinder.