4.3 Bleeding Brakes (ABS only)

In general, the same concerns about brake fluid and brake bleeding which apply to the conventional dual-diagonal braking system also apply to ABS-equipped cars. The ABS, however, requires some additional safety precautions and slightly different procedures.

The ABS operates at very high pressure-as much as 210 bar (3045 psi)-and is self-pressurizing. This pressure may be retained in the system even though the car is not running and has not been driven recently. Before beginning any brake work on an ABS-equipped car, the system must be depressurized. With the engine not running, depress the brake pedal 20 to 35 times to release the stored pressure from the accumulator. The reduction in pressure should be accompanied by a noticeable increase in pedal effort.

Once the stored pressure is bled from the system, the front brakes can be bled by conventional pressure bleeding or manual bleeding. See 4.2 Bleeding Brakes. Since the front brakes are operated by two completely independent hydraulic circuits, the order in which they are bled is unimportant.

The bleeding procedure for the rear brakes takes advantage of the ability of the ABS to pressurize itself. The hydraulic pump acts as a pressure bleeder. Bleed each of the rear brakes by depressing the brake pedal slightly, turning on the ignition (to run the hydraulic pump), and opening the bleeder valve. Allow the fluid to flow until it is clear and contains no air bubbles. Then close the bleeder valve and turn the ignition off. Repeat the procedure for the other rear brake. Finally, turn on the ignition and let the pump run until it shuts off.