Brake Bleeding: Service and Repair
Brake System, Bleeding
Special tools, testers and auxiliary items required
• Brake Filling and Bleeding Equipment (VAS5234)
• Upgrade kit and extraction unit (V.A.G1869/4)
• Tool Set For Brake Bleeding (VAS 6564)
• Vehicle Diagnosis, Testing and Information System (VAS5051)
Description covers bleeding of brake system using the brake filler and bleeder tool (VAS 5234).
• Bleeding the braking system on vehicles with ABS is carried out as for vehicles with conventional braking systems.
• Only use new brake fluid conforming to US-Norm FMVSS 116 DOT 4.
• Genuine VW/Audi brake fluid conforms to this specification.
• Brake fluid is poisonous. Due to its caustic nature, it must also never be brought into contact with paint.
• Brake fluid is hygroscopic, meaning that it absorbs moisture from the surrounding air, and must therefore be stored in air-tight containers.
• Rinse off any leaking brake fluid using plenty of water.
• There must be a positive pressure of 2 bar to bleed the ABS hydraulic unit (N55).
• On vehicles with ABS/ASR or ABS/EDS/ASR/ESP, the brake system must be pre-bled when a chamber in the brake fluid reservoir is completely empty.
Pre-bleeding
- Connect the (VAS 5234).
Bleeding sequence:
1 - Bleed the left front and right front brake calipers simultaneously.
2 - Bleed left rear and right rear brake caliper together simultaneously.
- With bleeder bottle hoses attached, leave bleeder valves open long enough that brake fluid exits without bubbles.
Next, use the (VAS5051) to bleed the ABS hydraulic unit (N55) one more time by setting the "basic setting".
Initiate basic setting (to bleed the brake system):
- (VAS 5051) , connecting and selecting functions. Refer to=> [ , Connecting and Selection Functions ] Testing and Inspection.
- Afterward, bleed the brake system normally.
Bleeding, Normal
Adhere strictly to work sequence when bleeding brake system.
- Connect the (VAS 5234).
- Open bleeder valves in the prescribed sequence and bleed brake caliper.
1- Front left brake caliper
2 - Right front brake caliper
3 - Left rear brake caliper
4 - Right rear brake caliper
• Use suitable bleeder hose. It must fit tightly on bleeder valve so that no air gets into brake system.
- With bleeder bottle hose attached, leave bleeder valve open long enough that brake fluid exits without bubbles.
Post-bleeding
A second mechanic is required to assist:
A technician has to sit in the driver seat the entire time so that the brake pedal does not get twisted.
- Press brake pedal forcefully and hold.
- Open bleeder valve at brake caliper.
- Press brake pedal down onto stop.
- Close bleeder valve with the pedal assembly pressed.
- Release brake pedal slowly.
• This bleeding procedure must be performed 5 times per brake caliper.
Bleeding sequence:
1- Front left brake caliper
2 - Right front brake caliper
3 - Left rear brake caliper
4 - Right rear brake caliper
• A road test must be performed after bleeding. During this, at least one ABS regulation must be performed!