Brake Bleeding: Service and Repair
Brake system, bleeding
WARNING!
^ Brake fluid must never be brought into contact with liquids containing mineral oils (e.g. oil, fuel, cleaning agents). Mineral oils damage the plugs and seals in the brake system.
^ Brake fluid is poisonous and must NEVER be removed by siphoning with your mouth. Due to its caustic effect it must also not be allowed to come into contact with paintwork.
^ Brake fluid is hydroscopic (i.e. it absorbs moisture from the surrounding air) and should therefore always be stored in airtight containers.
^ Always dispose of used brake fluid properly.
Notes:
^ Use only new brake fluid conforming to US standard FMVSS 116 DOT 4.
^ Genuine VW/Audi brake fluid conforms to this specification.
^ Rinse off any spilled brake fluid using plenty of water.
^ Do not work with compressed air and do not move vehicle while the system is open.
^ During final road test, at least one ABS-controlled braking operation must be performed (appropriate pulsations must be felt at brake pedal).
Bleeding brake system using US1116 brake filler/bleeder unit
- Connect US1116 brake filler/bleeder unit.
- Open bleeder valves in the prescribed sequence and bleed brake caliper.
Bleeding sequence
1. Right-rear brake caliper
2. Left-rear brake caliper
3. Right-front brake caliper
4. Left-front brake caliper
Bleeding procedure for vehicles with Electronic Stability Program (ESP)
Note the following:
- There must be a positive pressure of at least 2 bar (29 psi) to bleed the hydraulic pump. Therefore, always check pressure selling at the bleeder unit.
- First, all brake calipers are bled using the traditional method but in a different sequence.
- Then the hydraulic pump for ESP must be bled. This is done using the scan tool.
- The hydraulic pump will be activated for 10 seconds using the scan tool.
Special tools and equipment
- VAG1551 or VAG1552
- US1116 Brake bleeding unit
Bleeding brake system using US1116 brake filler/bleeder unit
- Connect US1116 brake filler/bleeder unit.
- Open bleeder valves in the prescribed sequence and bleed brake caliper (support with pedal pressure if necessary).
Bleeding sequence
1. Left-rear brake caliper
2. Right-front brake caliper
3. Right-rear brake caliper
4. Left-front brake caliper
- Bleed until brake fluid escapes free of bubble and foam.
- Close bleeder valve.
Connecting VAG1551 and selecting address word
Note: If VAG1551 Scan Tool is not available, use VAG1552 Mobile Scan Tool instead. However, the VAG1552 is not capable of printing out information.
- With the ignition off, connect scan tool using VAG1551/3 adapter cable to Data Link Connector (DLC) under the dash to the left of the steering column.
Indicated on display:
1. shown alternately
Notes: If nothing is indicated on display, check diagnostic connection.
^ The PRINT button is used for switching on the printer. Indicator lamp in the button comes on when printer is switched on.
^ Depending on the program, additional operating information can be printed out by pressing the HELP button of the VAG1551 scan tool.
- Switch ignition on.
- Switch printer on by pressing PRINT button on scan tool.
- Press button -1- to select "Rapid data transfer" operating mode 1.
- Press buttons -0- and -3- to select "Brake Electronics" address word 03 and press -Q- button to confirm.
- Press (arrow) button.
- Indicated on display:
- Press the -1- button twice to select the function "Login-Procedure."
- Indicated on display:
- Confirm input using the -Q- button.
- Indicated on display:
- Press buttons -4-, -0-, -1-, -6- and -8- to select code number 40163. Press -Q- button to confirm input.
- Indicated on display:
- Press buttons -0- and -4- to select function 04 "Basic Setting"
- Indicated on display:
- Confirm input using the -Q- button.
- Indicated on display:
- Left-front bleeder valve must be open while booster pump is being activated.
- Press buttons -0-, -0- and -2-.
- Press -Q- button to confirm input and the hydraulic pump for traction control -V156- will be activated for 10 seconds.
- Indicated on display:
- Close bleeder valve again.
- Press (arrow) button to return to beginning of troubleshooting procedure ("Select function XX" prompt).
- Indicated on display:
The rest of installation of the hydraulic pump for traction control occurs in reverse sequence.
Brake fluid, changing (every 2 years)
WARNING!
^ Brake fluid must never be brought into contact with liquids containing mineral oils (e.g. oil, fuel, cleaning agents). Mineral oils damage the plugs and seals in the brake system.
^ Brake fluid is poisonous and must NEVER be removed by siphoning with your mouth. Due to its caustic effect, it must also not be allowed to come into contact with paintwork.
^ Brake fluid is hydroscopic (i.e. it absorbs moisture from the surrounding air) and should therefore always be stored in airtight containers.
^ Always dispose of used brake fluid properly.
Notes:
^ Use only new brake fluid conforming to US standard FMVSS 116 DOT 4.
^ Genuine VW/Audi brake fluid conforms to this specification.
^ Rinse off any spilled brake fluid using plenty of water.
^ Do not work with compressed air and do not move vehicle while the system is open.
^ During final test, at least one ABS- controlled braking operation must be performed (appropriate pulsations must be felt at brake pedals.
Bleeding brake system using US1116 brake filler/bleeder unit
- Open brake fluid reservoir.
Note: Brake fluid reservoir must be kept adequately filled at all times to prevent air from entering the brake system through the reservoir.
- With engine running and bleeder valve on right-rear brake caliper open, use brake pedal to pump brake fluid out of reservoir until level goes down as far as opening for hydraulic clutch supply hose.
- Collect used brake fluid in suitable container. Close bleeder valve.
- On vehicles with manual transmission, the clutch slave cylinder must also be flushed out with new brake fluid.
Note the following for this procedure:
- Connect US1116 but do not switch on yet.
- Open bleeder valve on clutch slave cylinder.
- Attach collector bottle hose.
- Switch on bleeder unit and allow approximately 100 cc of brake fluid to flow out of clutch slave cylinder.
- Close bleeder valve.
The following sequence is valid for all four brake calipers.
1. Right-rear brake caliper
2. Left-rear brake caliper
3. Right-front brake caliper
4. Left-front brake caliper
- Attach bleeder hose from brake fluid collector to bleeder valve.
- Open bleeder valve and allow about 250 cc of brake fluid to drain out.
The action of pumping in new brake fluid flushes used brake fluid out of the system.
- Close bleeder valve.
- Check pedal pressure and brake pedal free play. Max. free play: 1/3 of pedal travel