Hydraulic Control Unit, Bosch 8.0

Hydraulic Control Unit, Bosch 8.0

Special tools, testers and auxiliary items required

• Torque wrench (V.A.G 1331)

• Brake pedal actuator (V.A.G 1869/2)

• Sealing plug repair kit (1H0 698 311 A)

Removing

The hydraulic unit is located on the left hand side of the engine compartment.





CAUTION!
Brake lines must not be bent.

- Note or request the radio code on vehicles with a coded radio if necessary.

- Disconnect the negative battery cable.

- Remove the plenum chamber cover.





- Remove the bolts - 1 - securing the coolant expansion tank.





- Disconnect the connector from the coolant expansion tank.

- Move the coolant expansion tank to one side.





- Insert the brake pedal actuator (V.A.G 1869/2 ) between the brake pedal and driver's seat. Depress the brake pedal at least 60 mm.





- Connect a bleeder bottle hose to the bleeder screws on the left front and rear brake calipers and open the bleeder screws.

• The pressure in the hydraulic unit is then released.

- Close the left front and rear bleeder screws.

- Do not remove the brake pedal actuator (V.A.G 1869/2).

- To protect against leaking brake fluid, place a lint free cloth in the area under the control module and hydraulic unit.

• Number the brake lines.

CAUTION!
Do not bend the brake lines in the area of the hydraulic unit!

- Disconnect the brake lines between the hydraulic unit and brake master cylinder.





- Disconnect the remaining brake lines - arrows - from the hydraulic unit.

- Seal the brake lines and threaded holes with sealing plugs from the Sealing plug repair kit (1H0 698 311 A).

- Open the brake line retainer - 1 -.





- Press the red locking slide upward.





• Make sure that no brake fluid gets into the control module connector housing. This could lead to corrosion of the contacts and thereby cause the system to fail.

• Clean a dirty connector housing thoroughly with compressed air.

- Release and disconnect the control module connector - arrow -.

- Push the retaining plate in the direction of - arrow - and disconnect connector.





- Remove the bolts - 1 -.





- Remove the hydraulic control unit.

Installing

Installation is in reverse order of removal. Note the following:

• Remove the sealing plugs on a new hydraulic unit when the corresponding brake line is going to be installed.

• If the sealing plugs are removed too early, brake fluid can leak, and can no longer be guaranteed that the unit is sufficiently filled or adequately bled.

- Connect the brake lines as previously marked:





1 Right front brake caliper
2 Left rear brake caliper
3 Right rear brake caliper
4 Left front brake caliper
5 Primary piston circuit
6 Secondary piston circuit

- Connect the connector onto the hydraulic pump.

- Clip the Antilock Brake System (ABS) unit onto the bracket.

• Do not tighten the bolts completely. This will make attaching the individual brake lines easier.

- After tightening the brake lines, tighten the hydraulic unit.

- Remove the brake pedal depressor (V.A.G 1869/2 ).

- Bleed the brake system. Refer to => [ Brake System Bleeding ] Brake System Bleeding.

- Code the ABS control module (J104).

- When replacing the control module, select function "Replacing " for the respective control module in "Guided Fault Finding ".

For this, use vehicle diagnosis, testing and information system (VAS 5051).

- After fastening the brake lines to the hydraulic unit, perform the final control diagnosis.

• Final control diagnosis can be used to establish whether line connections have been interchanged. Refer to => [ Front Axle ABS Component Overview ] Front Axle ABS Component Overview.

Tightening Specifications