VW Golf manuals

Volkswagen Golf Service & Repair Manual: General information

Repair instructions for repair work on ABS

The ABS brake system is divided diagonally. The servo-assistance is effected pneumatically by the vacuum brake servo unit.
Vehicles with ABS are not fitted with a mechanical brake pressure regulator. Specially developed software in the control unit regulates the brake force distribution on the rear axle.
  Note
Faults in the ABS do not influence the brake system and servo assistance. The conventional brake system remains functional even without ABS. A change in braking behaviour is to be reckoned with. After the ABS warning lamp comes on, the rear wheels may lock prematurely during braking.
   
ABS layout in LHD vehicles:
1 -  Hydraulic unit and control unit
2 -  Brake servo
The control unit and hydraulic are combined in a single component. They can be separated only when removed. Hydraulic pump must not be separated from hydraulic unit either.
 

Repair instructions for repair work on ABS

ABS layout in RHD vehicles:
1 -  Brake servo and brake master cylinder
2 -  ABS hydraulic unit -N55- and ABS control unit -J104-
The control unit and hydraulic are combined in a single component. They can be separated only when removed. Hydraulic pump must not be separated from hydraulic unit either.
Before carrying out repair work on the anti-lock brake system, determine the cause of the fault as well as the control unit code using “Guided Fault Finding”.
“Guided fault finding” is carried out using → Vehicle diagnostic tester.
Disconnect battery earth strap with ignition switched off.
Before carrying out welding work with an electric welding unit, note → General Information; Body Repairs, General Body Repairs.
When working with brake fluid, observe the relevant safety precautions and notes → Chapter.
After work for which the brake system had to be opened, bleed the brake system with brake filling and bleeding equipment -VAS 5234- → Chapter.
During the final road test, ensure that a controlled brake test is performed at least once (pulsations must be felt at the brake pedal).
Absolute cleanliness is required when working on the anti-lock brake system. Auxiliary items containing mineral oil, e.g. oils, greases, etc. must never be used.
Thoroughly clean all unions and the adjacent areas before loosening. Do not use aggressive cleaning agents such as brake cleanser, petrol, thinners or similar.
Place removed parts on a clean surface and cover.
If repairs cannot be carried out immediately, carefully cover or seal open components. (Use sealing plugs from repair kit 1 H0 698 311 A).
Only use lint-free cloths.
Only unpack replacement parts immediately prior to fitting.
Only use genuine packed parts.
When the system is open, do not work with compressed air and do not move the vehicle.
The valve coils in the control unit cannot be adjusted.
The valve coils in the control unit cannot be renewed.
Pressure sensor must not be changed or damaged.
The pressure sensor cannot be renewed.
The sensor housing must not be exposed to mechanical stress.
No measurements must be taken on contact points of control unit.
No measurements must be taken on contact points of hydraulic unit.
Contact pins of hydraulic unit must not be bent or damaged.
The contacts cannot be renewed.
No contact sprays may be used on the contacts or the pressure sensor.
Foreign bodies must not get between the control unit and the hydraulic unit.
During painting operations, the electronic control unit can be exposed to a maximum temperature of 95°C for only a short period, and to a maximum of 85°C for longer periods (approx. 2 hours). During longer periods (2 hours), the control unit can be exposed to a maximum temperature of 85°C. Ensure that no brake fluid enters connectors.
 

Repair instructions for repair work on ABS

ABS, ADR, TCS, EDL, ESP
...

Overview of fitting locations
Overview of fitting locations - ABS/ESP 1 -  ABS control unit -J104- Installation location: on hydraulic unit, on passenger side in engine compartment. ...

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