Anti-Lock Brake Repair Information
The anti-lock brake system is generally maintenance-free.
Testing, assembly, and repair work may only be performed by qualified personnel.
By not observing the points described in the repair information, the system can be damaged and vehicle safety could be compromised.
The ABS brake system is divided diagonally (two circuits). The vacuum brake servo unit boosts the brakes pneumatically.
Vehicles with ABS Mark 60 do not have a mechanical brake pressure regulator. A specially coordinated software program in the control module determines brake pressure allocation at the rear axle.
ABS disturbances do not affect the brake system and the booster. Conventional brake system stays operative even without ABS. A change in braking behavior should be checked. When the ABS warning lamp comes on the rear wheels can lock-up early when braking!
- Before performing repair work on the anti-lock brake system, determine the cause of the malfunction using On-Board Diagnostics (OBD).
- The connector at the hydraulic control unit may only be disconnected if the ignition is switched off.
- When installing a new hydraulic control unit, it must be coded Vehicle diagnosis, test, and information system VAS 5051 B or VAS 5052.
- After performing work that required the brake system to be opened, bleed the brake system: ABS/ESP Mark 60/ ABS Mark 70. Refer to BLEEDING BRAKE SYSTEM, ITT ABS/ESP MARK 60/ ABS MARK 70 . To do this, use for example the brake filler/bleeder unit VAS 5234.
- When working with brake fluid, observe relevant safety precautions and notes.
- Absolute cleanliness is required when working on the anti-lock brake system, it is not permitted to use any products which contain mineral oil, such as oils, greases etc.
- Make sure that brake fluid does not enter harness connectors.
- Thoroughly clean all unions and the adjacent areas before loosening. Do not use aggressive cleaning agents such as brake cleaner, fuel, thinners or similar chemicals.
- Place parts that have been removed on a clean surface and cover.
- Carefully cover over opened components or seal, if repairs are not carried out immediately. Use sealing plugs from repair kit; Part No.
- Do not work with compressed air and do not move vehicle while the system is open.
- Only use lint-free cloths.
- Only use parts in their original packaging.
- Only unpack replacement parts immediately prior to installation.
- During the final road test, ensure that a ABS-controlled brake test is performed at least once (pulsation must be felt at the brake pedal).
- When painting, electronic control module can be exposed to a maximum temperature of. 95 °C (203 °F) only briefly, and to a maximum of 85 °C (185 °F) for longer periods (approximately 2 hours).
- Before welding operations using an electric welding device.