Hydraulic Control Assembly - Antilock Brakes: Service and Repair

Hydraulic Unit, Bosch 5.7

Special tools, testers and auxiliary items required

• Torque wrench (V.A.G 1331/)

• Brake pedal actuator (V.A.G 1869/2)

• Vehicle Diagnosis, Testing and Information System (VAS 505x)

• Sealing plugs repair kit part no. 1H0 698 311A

Component Location





Hydraulic unit is located at left of engine compartment.

Removing


Brake lines must not be bent.

- Switch ignition off.

- Remove coolant reservoir hex bolts - 1 -.





- Remove hex bolts - 1 -.





- Disconnect connector from reservoir.

- Lay aside reservoir.

- Remove power steering fluid reservoir hex bolt - 1 - and remove sideways from rubber bushing.





- Disconnect connector - 1 - from brake pressure sensor.





- Install (V.A.G 1869/2) between the brake pedal and driver seat. Depress the brake pedal a minimum of 60 mm.





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

• This lowers the pressure in the hydraulic unit.

- Close the left front and left rear bleeder screws.

- Do not remove (V.A.G 1869/2).

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

- Mark the brake lines.

- Remove brake lines from hydraulic unit to brake master cylinder - 3 - and tie up.





- Remove the remaining brake lines - 2 - from hydraulic unit.


Do not bend the brake lines near the hydraulic unit.

- Seal the brake lines and threaded bores with sealing plugs from the repair set.

- Release connector at control module - arrow - and remove.





• 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 locking clip - 1 - on both sides from below.





- Remove locking clip in - direction of arrow -.





- Remove hydraulic control unit.

Installing

Installation is the reverse of removal, with special attention to the following:

• Do not remove sealing plugs at new hydraulic unit until the corresponding brake line is about to be installed.

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

- When fitting together the control module and hydraulic unit, make sure that the valve body of the hydraulic unit does not bind with the solenoid coils of the control module.

- Connect lines according to identification:





1 Primary piston circuit
2 To left front brake caliper
3 To right front brake caliper
4 Secondary piston circuit
5 To left rear brake caliper
6 To right rear brake caliper

- Connect connector at hydraulic pump.

- Clip ABS unit to bracket.

• Do not tighten bolts completely. This makes it easier to fasten the individual brake lines to the hydraulic unit.

- After fastening the brake lines, fasten the hydraulic unit.

- Remove (V.A.G 1869/2).

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

- Code ABS Control Module (J104) via Guided fault finding function using the (VAS 505x).

- If control module is replaced, select "Replace" function for respective control module in Guided Fault Finding.

- After fastening the brake lines to the ABS hydraulic unit, perform the output check diagnosis via Guided fault finding function using the (VAS 505x).

• By performing the output check diagnosis, it can be determined if the line connections were interchanged.

Tightening Specifications