Procedures

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 hydraulic unit N55 must be prefilled for Service.

• Brake fluid must never come into contact with fluids containing mineral oils (oil, gas, cleaning solutions). 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.

• 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.

• There must be a positive pressure of 2 bar to bleed the 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

• (VAS 5234) Brake charger/bleeder unit

• (VAS 5234/1) Adapter

Bleed the brake system with the brake charger/bleeder unit VAS 5234 with the adapter VAS 5234/1

Follow the (VAS 5234) operating instructions.

- Remove the plenum chamber cover => 50.

- Raise the vehicle.

- Connect the (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

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 the bleeder screws.

- Lower vehicle.

- Install plenum chamber cover => 50.