Brake System Bleeding
Fig. 22 Booster Bleeding:
Any time air is allowed to enter the brake system, due to damage or service, the system must be bled. Air in the system will not cause a spongy pedal, but instead may set a trouble code.
When bleeding brakes, maintain an appropriate level of DOT 3 brake fluid, and do not allow the pump/motor assembly to run continuously for more than 60 seconds. If it becomes necessary to run the pump for more than 60 seconds, allow it to cool for several minutes before running it again.
BOOSTER BLEEDING
1. Depressurize hydraulic accumulator as follows:
a. Disconnect battery ground cable, and ensure ignition is in the OFF position.
b. Pump the brake pedal at least 25 times with about 50 lbs. of force. A noticeable change in pedal feel should be evident.
c. When a definite increase in pedal effort is felt, pump pedal a few more times to remove hydraulic pressure from lines.
2. Connect battery negative cable.
3. Check that all brake lines and hoses are tight, and fill fluid reservoir.
4. Connect a transparent hose to the bleeder screw, and place the other end into a clear container to hold brake fluid.
5. Open bleeder screw 1/2 -3/4 of a turn.
6. Turn on the ignition switch ON, to force fluid out the open bleeder. When the fluid flowing from the tube is clean, and free of air bubbles, turn ignition OFF. If fluid does not flow when ignition is turned ON, the pump may need to be primed. First try shaking the pump return hose, with the ignition still on to break up air bubbles. If necessary, turn ignition OFF, remove pump return hose at one end, fill with brake fluid and reconnect. Attempt bleeding operation again.
7. Remove bleeder hose, and torque bleeder screw to 7.5 lb-ft Do not over torque.
8. Top off reservoir to correct level, then turn on ignition to allow pump to charge the accumulator. The pump should stop after about 30 seconds.
Fig. 23 Pressure Bleeding:
Fig. 24 Bleeding Brake At Caliper:
PRESSURE BLEEDING
The brake lines can be bled using a standard diaphragm type pressure bleeding system. Use only a diaphragm type system to prevent contaminants from entering the system.
1. Ensure ignition remains off for the entire procedure.
2. Depressurize the hydraulic accumulator as outlined under "Booster Bleeding."
3. Disconnect electrical connector from fluid level sensor, then remove reservoir cap.
4. Install pressure bleeder adapter, then attach bleeding equipment to adapter. Charge pressure bleeder to 20 psi.
5. Connect a transparent hose to caliper bleed screw, and submerge the other end in a clear container, partially filled with clean brake fluid.
6. Turn pressure bleeder on, then open caliper bleed screw 1/2-3/4 turn allowing fluid to escape until no more air bubbles are present. If reservoir has been drained, or hydraulic assembly removed prior to bleeding, pump the brake pedal slowly one or two times with bleed screw open to purge air from hydraulic assembly.
7. Repeat step 6 for each caliper in the following order: LR-RR-LF-RF.
8. After bleeding all calipers, close the pressure bleeder valve and torque to 7.5 lb-ft, then slowly unscrew the bleeder adapter from the hydraulic assembly reservoir.
9. Use a syringe or other method to remove excess fluid from reservoir and adjust to the full mark.
10. Install reservoir cap, connect the fluid level sensor connector, and turn on ignition to allow pump to charge the accumulator.
MANUAL BLEEDING
1. Depressurize the hydraulic accumulator as outlined under "Booster Bleeding."
2. Connect a transparent host to caliper bleed screw, and place the other end of hose in a transparent container partially filled with clean brake fluid.
3. Slowly pump brake pedal several times with full strokes of the brake pedal. Allow about five seconds between pedal strokes. After two or three strokes, continue holding pedal under pressure at the bottom of its travel.
4. Open the bleed screw 1/2-3/4 turn. Keep screw open until fluid no longer comes out from bleeder, then tighten bleeder screw and release brake pedal.
5. Repeat this procedure until air bubbles are no longer present in fluid coming from bleeder hose.
6. Repeat for all wheels in the following order: LR-RR-LF-RF.