Hydraulic Control Assembly - Antilock Brakes: Service and Repair
ABS Hydraulic Control Unit
Special tools, testers and auxiliary items required
• Torque Wrench (V.A.G 1410)
• Brake Pedal Actuator (V.A.G 1869/2)
Sealing Plug Repair Set, Part No. 1H0 698 311 A
After separating the control module from the hydraulic unit, the transport protection for valve body must be placed on the hydraulic unit.
Warranties will not be granted for hydraulic units without transport protection.
1 Transport protection for valve domes (foam)
2 Sealing plug M 10
3 Sealing plug M 12
Component location:
The control module is bolted to the hydraulic unit and is located at right in the plenum chamber.
Do not bend the brake lines near the hydraulic unit.
Control Module and Hydraulic Unit, Removing
- On vehicles with a coded radio, note the code. Retrieve it if necessary.
- Disconnect battery.
- Release control module connector - arrow 1 - and pull off - arrow 2 -.
- Insert (V.A.G 1869/2).
- Attach the bleeder bottle bleed hose - 1 - to the left front brake caliper bleed valve.
- Open the bleed valve.
- Attach the bleeder bottle bleed hose - 1 - to the left rear brake caliper bleed valve.
- Open the bleed valve.
- Depress the brake pedal at least 60 mm with the (V.A.G 1869/2).
- Close left front and left rear bleeder valves.
- Do not remove (V.A.G 1869/2).
- Place sufficient lint-free cloths under the control module and hydraulic unit.
• Make sure that brake fluid does not come in contact with the terminals.
- Open and remove the left and right brake line bracket from the hydraulic unit.
- Identify brake lines and remove at hydraulic unit.
- Seal brake lines and threaded holes with (1H0 698 311 A).
- Remove the hydraulic unit and control module from the shock absorbers.
- Remove the hydraulic unit from the bracket.
Control Module, Removing from Hydraulic Unit
- Set hydraulic unit with control module upward onto a clean, level surface.
- Remove the inner Torx(R) bolt from the control module.
- Pull control module off from hydraulic unit - arrow - without angling.
• On a disconnected control module, circuit board is laid open.
• No moisture or dirt particles must get into the control module.
• Avoid build-up of static electricity!
- Cover control module magnetic coils with a lint free cloth.
• After separating the control module and hydraulic unit, use transport protection for valve body.
New Control Module, Installing
Excessive shaking (e.g. dropping, impact) may destroy the control module. Control module must then no longer be used.
• Surface must be cleaned before assembling.
• Use new bolts.
• A new control module may be installed a maximum of two times to a used hydraulic unit, to ensure that the elastic gasket seals sufficiently.
• Do not install a used control module.
- Carefully push the control module onto the hydraulic unit, without tilting it.
- Install the hydraulic unit and control module with the new inner Torx(R) bolts diagonally according to the tightening specification.
Control Module and Hydraulic Unit, Installing
• Do not remove sealing plugs at new hydraulic unit until the corresponding brake line is about to be installed.
• If the sealing plugs are removed too early, brake fluid can escape and unit may not be sufficiently filled or adequately bled.
- Install in reverse order of removal.
- Spray the rubber bushings with silicone lubricant spray D 007 000 A2 before installing the bracket for the ABS hydraulic unit (N55).
When installing the bracket, be careful not to push rubber insulation. After installing, make sure the hydraulic unit and the control module are secure, otherwise malfunctions will register.
- Remove (V.A.G 1869/2).
- Bleed the brake system. Refer to => [ Brake System, Bleeding ] Brake System, Bleeding.
- Enter radio code.
- Perform ABS control module (J104) coding using Vehicle diagnosis, testing and information system (VAS 5051) in "Guided Fault Finding".
- Perform a basic setting after replacing the ABS control module.
