The master cylinder reservoirs must be kept properly filled to prevent air from entering the system. No special filling procedures are required because of the anti-lock system.
When adding fluid, use only DOT 3 fluid; the use of DOT 5 or silicone fluids is specifically prohibited. Use of improper or contaminated fluid may cause the fluid to boil or cause the rubber components in the system to deteriorate. Never use any fluid with a petroleum base or any fluid which has been exposed to water or moisture.
Before bleeding the ABS brake system, the front and rear displacement cylinder pistons must be returned to the topmost position. If brake related DTC's are present, the vehicle must be repaired and DTC's cleared before performing the motor rehome function.Rehome Procedure
- Rasie and safely support the vehicle on jackstands so that the drive wheels are off the ground.
- Start the engine, engage the transmission and run the vehicle above 3 mph (5 km/h) for at least 10 seconds.
- Observe the ABS light on the instrument panel. Be sure that indicator light goes out after approximately 3 seconds. If the ABS light remains illuminated, the TECH-1 scan tool (or equivalent) must be used to diagnose the malfunction. If the ABS light goes out and stays off, stop the engine and repeat Steps 2 and 3 once again.
- Using a Tech 1® or T-100® (CAMS), select "F5: Motor Rehome.'' The motor rehome function cannot be performed if current DTC's are present. If DTC's are present, the vehicle must be repaired and the codes cleared before performing the motor rehome function.
- The entire brake system should now be bled using the manual bleeding procedures outlined later in this section.
See Figures 1 and 2
- Clean the master cylinder fluid reservoir cover and surrounding area, then remove the cover.
- Add fluid, if necessary to obtain a proper fluid level, then put the reservoir cover back on.
Prime the ABS hydraulic modulator/master cylinder assembly as follows:
Attach a bleeder hose to bleeder valve (A) on the ABS hydraulic modulator, then submerge the opposite hose end in a clean container partially filled with clean brake fluid.
- Slowly open bleeder valve (A) one half to one full turn.
- Depress and hold the brake pedal until the fluid begins to flow.
- Close the valve, then release the brake pedal.
- Repeat Steps 3b-3d until no air bubbles are present.
- Relocate the bleeder hose to bleeder valve (B), then repeat Steps 3a-3e.
- Attach a bleeder hose to bleeder valve (A) on the ABS hydraulic modulator, then submerge the opposite hose end in a clean container partially filled with clean brake fluid.
- Once the fluid is seen to flow from both modulator bleeder valves, the ABS modulator/master cylinder assembly is sufficiently full of fluid. However, it may not be completely purged of air. At this point, move to the wheel brakes and bleed them. This ensures that the lowest points in the system are completely free of air and then the assembly can purged of any remaining air.
- Remove the fluid reservoir cover. Fill to the correct level, if necessary, then fasten the cover.
- Raise and safely support the vehicle.
Proceed, as outlined in the following steps, to bleed the wheel brakes in the following sequence: left rear, right front, then left front.
- Attach a clear plastic bleeder hose to the bleeder valve at the wheel, then submerge the opposite hose end in a clean container partially filled with clean brake fluid.
- Open the bleeder valve.
- Have an assistant slowly depress the brake pedal.
- Close the valve and slowly release the release the brake pedal.
- Wait 5 seconds.
- Repeat Steps 7a-7e until the brake pedal feels firm at half travel and no air bubbles are observed in the bleeder hose. To assist in freeing the entrapped air, tap lightly on the caliper or braking plate to dislodge any trapped air bubbles.
- Repeat Step 7 for the remaining brakes in the sequence given earlier.
- Carefully lower the vehicle.
- Remove the reservoir cover, then fill to the correct level with brake fluid and replace the cap.
Bleed the ABS hydraulic modulator as follows:
- Attach a clear plastic bleeder hose to the rearward bleeder valve on the modulator, then submerge the opposite hose end in a clean container partially filled with clean brake fluid.
- Have an assistant depress the brake pedal with moderate force.
- Slowly open the rearward bleeder valve one half to one full turn, and allow the fluid to flow.
- Close the valve, then slowly release the brake pedal.
- Wait 5 seconds.
- Repeat Steps 14b-14e until no air bubbles are present.
- Relocate the bleeder hose to the forward hydraulic modulator bleeder valve, then repeat Steps 11a-11f.
- Check the brake fluid and add if necessary. Don't forget to put the reservoir cap back on.
- With the ignition turned to the RUN position, apply the brake pedal with moderate force and hold it. Note the pedal travel and feel. If the pedal feels firm and constant and the pedal travel is not excessive, start the engine. With the engine running, recheck the pedal travel. If it's still firm and constant and pedal travel is not excessive, go to the next step.
If the pedal feels soft or has excessive travel either initially or after the engine is started, the following procedure may be used:
- With the Tech 1® scan tool, "release'' then "apply'' each ABS motor 2-3 times and cycle each ABS solenoid 5-10 times. When finished, be sure to "apply'' the front and rear motors on the ABS hydraulic modulator. This will ensure all trapped air has been removed from the hydraulic modulator bores.
- Repeat the bleeding procedure, starting with Step 1.
- Road test the vehicle. Make several normal (non-ABS) stops and from a moderate speed to be sure the brakes are operating properly.