Brake Bleeding: Service and Repair
WARNING:
^ NEVER bring brake fluid into contact with fluids containing mineral oil (oil, gasoline, cleaning fluids). Mineral oils damage plugs and boots in the brake system.
^ Brake fluid is poisonous. NEVER siphon brake fluid with your mouth! Due to its caustic nature, it must also never be brought into contact with paint.
^ Brake fluid is hydroscopic, meaning that it absorbs moisture from the surrounding air, and must therefore be stored in airtight containers.
^ Observe disposal regulations.
Note:
^ 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, carry out at least one ABS-controlled braking operation (appropriate pulsations must be felt at brake pedal).
-- Note also the information regarding road tests.
Bleeding brake system using US1116 brake bleeder
- Connect US1116 brake bleeder
- Open bleeder screws in the prescribed sequence and bleed brake caliper.
Bleeding sequence
1. Rear right brake caliper
2. Rear left brake caliper
3. Front right brake caliper
4. Front left brake caliper
- Bleed until bubble and foam-free brake fluid escapes.
- Close bleeder screw.
Bleeding procedure for vehicles with Electronic Stability Program (ESP)
Note:
There must be a positive pressure of at least 2 bar to bleed the hydraulic pump. Therefore, always check pressure setting 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.
Do not activate more than three times in a row (approx.30 seconds). After this, a cooling time of at least 5 minutes is necessary.
Special Tools and Equipment
^ VAG 1551 or VAG 1552
^ US1116 brake bleeder
Bleeding sequence
1. Rear left brake caliper
2. Front right brake caliper
3. Rear right brake caliper
4. Front left brake caliper
- Bleed until bubble and foam-free brake fluid escapes.
- Close bleeder screw.
Connecting VAG1551 and selecting address word
Note: If VAG 1551 Scan Tool (ST) is not available, use VAG1552 Mobile Scan Tool (ST) instead. The VAG1552 is not capable of printing out information, however.
- Disengage ashtray and remove from center console.
- Remove cover for Data Link Connector (DLC).
- Connect scan tool to Data Link Connector (DLC) with the ignition off using VAG1551/3 adapter cable.
Indicated on display:
1. Appears alternately on display
Note:
^ If nothing is indicated on display, check diagnostic connection.
Refer to Electrical Wiring Diagrams
^ 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.
Indicated on display:
^ Press buttons -O- and -3- for address word "Brake electronics".
Indicated on display:
- Confirm input using the -Q- button.
Rapid data transfer Scan tool sends address word 03
Indicated on display after entering address word 03:
Note: If communication cannot be established between the VAG1551 Scan Tool (ST) and control module:
Refer to Powertrain Management, Basic information regarding On Board Diagnostic (OBD); VAG1551 Scan Tool (ST), connecting and selecting address words
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:
- Open vent screw at front left brake caliper.
- Press buttons -0-, -0-, and -2-. Press -Q- button to confirm input.
Indicated on display:
Note:
The hydraulic pump for traction control -V166- is activated for ten (10) seconds.
Do not activate more than three times in a row (approximately 30 seconds). After this, a cooling time of at least 5 minutes is necessary.
To interrupt activation, press the (arrow) button. The program will return to the start screen.
Indicated on display:
- Bleed until bubble and foam-free brake fluid escapes.
- Close bleeder screw.
- Press buttons -0- and -6- to select "End Output" function 06.
Indicated on display:
- Confirm input using the -Q- button.
Indicated on display:
- Switch ignition off.
- Disconnect scan tool.
- Switch off US1116 brake bleeder.
- Check brake fluid level in expansion tank, correct if necessary.