Antilock Brakes / Traction Control Systems: Service and Repair

NOTE: Read the notes relating to the ABS system bleed procedure before commencing this operation.
Under ideal conditions this test should be carried out at 20° C room temperature.

1. Discharge the system by operating the brake pedal approximately 20 times.

High Pressure Line:

2. Disconnect the bundy pipe from the motor/pump unit.

Hydraulic Adaptor:

3. Fit the hydraulic adaptor to the high pressure outlet.
4. Raise car on a lift.

Bleed Valve Adaptor:

5. Remove the bleed nipples and fit adaptors to both front brake calipers.

Rear Bleed Valve Adaptor:

6. Remove the bleed nipple and fit an adaptor to one rear brake caliper.
7. Lower the ramp.
8. Connect the flexible pipe to the 250 bar gauge. Connect the other end to the adaptor on the motor pump unit, noting the different threads.

CAUTION: Always connect the flexible pipe to the gauge first, then to the adaptor.

9. Switch the ignition ON position 2 and note the following:
a. Immediate reading up to approximately 80 bar.
b. Elapsed time when the Brake and ABS warning lights go out; up to a maximum of 40 seconds with an approximate 1 second differential between the two lights.
c. Reading on the pressure gauge should be 125 bar.
d. Elapsed time when the pump cuts out; up to a maximum of 60 seconds.
e. Reading on the pressure gauge should be no more than 190 bar.

10. Be sure that the hydraulic circuit is pressurized, pump is not running, and the ignition is ON position 2.
11. Press and hold the brake pedal.
12. Reading on the pressure gauge when the pump is activated should be 140 bar. The pressure should be restored to 180 bar.
13. Release brake pedal.
14. The pressure should then be restored to 190 bar.
15. Switch the ignition OFF position 0.
16. Remove the pump/motor fuse.
17. Switch the ignition ON position 2.
18. Press the brake pedal hard approximately 7 times.
19. Note the reading on the pressure gauge when the warning light comes on. Should be approximately 105 bar.
20. Continue pressing the pedal approximately 20 times until the pressure gauge reads 0 bars.
21. Switch the ignition OFF position 0.
22. Refit the pump/motor fuse.
23. Switch the ignition ON position 2, and wait until maximum pressure is reached. Should be 190 bar.
24. Switch the ignition OFF (position 0), and wait 3 minutes for the pressure to stabilize.
25. Reset the 'tell-tale' needle on the pressure gauge.
26. After 5 minutes has elapsed, check that the pressure leak is no more than 10 bar.
27. Remove the gauge and flexible pipe from the motor/pump unit. Raise the ramp.
28. Connect the second flexible pipe to the second pressure gauge. Connect both flexible pipes to the adaptors.
29. Lower the ramp.
30. Switch the ignition ON (position 2), and wait until maximum pressure is attained (up to 60 seconds).
31. Switch the ignition OFF (position 0).

Holding Brake Pedal:

32. Position the brake pedal operating tool (Fig 1) and adjust the knurled nut until both pressure gauges read 100 bar.
33. Wait 3 minutes for the pressure to stabilize.
34. Reset the 'tell-tale' needle on both pressure gauges.
35. After 5 minutes has elapsed, check that the pressure leak is no more than 5 bar.
36. Remove the brake pedal operating tool.
37. Leaving one front gauge still in circuit, transfer a flexible pipe and pressure gauge to the rear adaptor. Switch the ignition ON (position 2), and wait (up to a maximum of 60 seconds) until maximum pressure is attained - 180 bar.
38. Switch the ignition off (position 0).
39. Position the brake pedal operating tool and adjust the knurled nut until the rear pressure gauge reads 100 bar.

NOTE: The front and rear systems should differ by no more than 8.5 bar (higher on the front system).

40. Wait 3 minutes for the pressure to stabilize.
41. Reset the 'tell-tale' needle on both pressure gauges. After 5 minutes has elapsed, check that the pressure leak is no more than 5 bar.
42. Remove the brake pedal operating tool.
43. Discharge the system, refit the bleed nipples and high pressure hose.
44. Bleed the ABS hydraulic system. Check system for external leaks.

NOTE: Any faults found during the pressure test should be referred to the HYDRAULIC SYSTEM FAULT DIAGNOSIS CHART for identification and remedy.