Brake Bleeding: Service and Repair

Brake System, Bleeding


• Do not, under any circumstances, allow brake fluid to come into contact with any fluids containing mineral oil (oil, gasoline, cleaning solvents). Mineral oil damages the sealing plugs and boots of the brake system.

• Brake fluid is poisonous. NEVER siphon brake fluid with your mouth! Also due to its corrosive effect, brake fluid must not come into contact with paintwork.

• Brake fluid is hygroscopic, meaning that it absorbs moisture from the surrounding air, and must therefore be stored in air-tight containers.

• When bleeding, brake fluid that has been flushed through must not be reused and must be disposed of properly.

• Observe disposal regulations. Refer to => [ Brake Fluid ] Description and Operation.

• Only use new brake fluid conforming to US-Norm FMVSS 116 DOT 4.

• Genuine VW/Audi brake fluid conforms to this specification.

• Do not use any silicone-based fluid.

• Avoid contaminating brake fluid with particles or lint (e.g. from cleaning cloths).

• Rinse off spills, by using plenty of water.

• Do not work with compressed air and do not move vehicle while the system is open.

• During the final road test, ensure that a ABS-controlled brake test is performed at least once (pulsation must be felt at the brake pedal).

• The brake system indicator light blinks when the brake fluid is too low or the ABS system or parking brake is malfunctioning.

Bleeding Procedure


To make sure the brake system and the brake control system function properly, the entire brake system and hydraulic components must be bled correctly. The ABS Hydraulic Unit (N55) must be prefilled for Service.

• There must be a positive pressure of 2 bar to bleed the ABS Hydraulic Unit (N55). Pressure setting must be checked at bleeder device.

• Only place brake pedal load device on brake system during assembly, then bleed.

Special tools, testers and auxiliary items required

• Brake filler/bleeder unit (VAS 5234)

• Adapter (VAS 5234/1)

Bleed the brake system with the Brake filler/bleeder unit (VAS 5234) with the Adapter (VAS 5234/1)

Follow the Brake filler/bleeder unit (VAS 5234) operating instructions.

- Remove plenum chamber cover.

- Raise vehicle.

- Connect Brake filler/bleeder unit (VAS 5234) with Adapter (VAS 5234/1).

- Open the bleeder screws in the specified sequence and bleed (support with pedal pressure if necessary).

Bleeding sequence


Each brake caliper with two bleeder screws. To achieve optimum brake system bleeding, bleed the respective brake caliper at both bleeder screws. Always bleed the outer screw first, then the inner one.

1 Left front brake caliper
2 Right front brake caliper
3 Left rear brake caliper
4 Right rear brake caliper.

- Bleed until brake fluid comes out with no bubbles and foam.

- Close bleeder screws.

- Lower vehicle.

- Install plenum chamber cover.