Pressure Bleeding (Preferred Procedure)

The anti-lock brake system must be bled any time air is permitted to enter the hydraulic system, due to disconnection of brake lines or hose for service. It is important to note that air in the hydraulic system will not cause a spongy pedal feel or additional pedal travel. The Bosch anti-lock brake system monitors booster piston travel and booster pressure and may set a diagnostic trouble code, due to air in the brake system.

The brake lines may be pressure bled, using a standard diaphragm type pressure bleeder. Only diaphragm type pressure bleeding equipment should be used to prevent air, moisture, and other contaminants from entering the system. The following procedure should be used for pressure bleeding of the master cylinder and wheel circuits:

1. Ignition should be turned off and remain off throughout this procedure.
2. Depressurize the hydraulic accumulator by pumping the brake pedal a minimum of 25 times, as described in this section.

WARNING: Failure to depressurize hydraulic accumulator, prior to performing this operation, may result in personal injury and/or damage to painted surfaces.

3. Remove electrical connector from fluid level sensor on reservoir cap and remove reservoir cap.

Fig. 46 - Pressure Bleeding:

4. Install pressure bleeder adapter, as shown.
5. Attach bleeding equipment to bleeder adapter. Charge pressure bleeder to approximately 20 psi (138 kPa).

Fig. 47 - Bleeding Brake System:

6. Connect a transparent hose to the caliper bleed screw. Submerge the free end of the hose in a clear glass container, which is partially filled with clean, fresh brake fluid.
7. With the pressure bleeder turned on, open the caliper bleed screw 1/2 to 3/4 turn and allow fluid to flow into the container. Leave bleed screw open until clear, bubble-free fluid flows from the hose. If the reservoir has been drained or the hydraulic assembly removed from car prior to the bleeding operation, slowly pump the brake pedal one or two times while the bleed screw is open and fluid is flowing. This will help purge air from the hydraulic assembly. Tighten bleeder screw to 7.5 ft.lbs. (10 Nm).
8. Repeat step 7 at all calipers. Calipers should be bled in the following order:
a. Left rear
b. Right rear
c. Left front
d. Right front
9. After bleeding at all four calipers, remove the pressure bleeding equipment and bleeder adapter by closing the pressure bleeder valve and slowly unscrewing the bleeder adapter from the hydraulic assembly reservoir. Failure to release pressure in the reservoir will cause spillage of brake fluid, and could result in injury or damage to painted surfaces.
10. Using a syringe or equivalent method, remove excess fluid from the reservoir to bring the fluid level to full level.
11. Install the reservoir cap and connect the fluid level sensor connector. Turn ignition on and allow pump to charge the accumulator.