Brake System Bleed

Bleeding Wheel Cylinder/Caliper (Typical):

CAUTION:
^ Use only Delco Supreme 11(r) Brake Fluid, GM P/N 1052535, or equivalent DOT 3 brake fluid from a clean, sealed container.
^ Do not use any fluid from a container which is wet with water.
^ Do not use DOT 5 silicone brake fluid.
^ Improper brake fluid, water, or mineral oil in the fluid may cause the brake fluid to boil or the rubber components to deteriorate.

NOTE:
^ If any brake component is repaired or replaced such that air is allowed to enter the brake system, the entire bleeding procedure MUST be followed.
^ Clean Master cylinder reservoir cap and surrounding area.

PROCEDURE
1. Remove master cylinder reservoir cap; inspect brake fluid level in reservoir and fill to the correct level if necessary. Make sure to replace the master cylinder reservoir cap.
2. Prime hydraulic modulator as follows:
a. Attach a clear plastic bleed hose to the rearward bleeder valve on the hydraulic modulator. Submerge the other end of the bleeder hose in a clean container partially filled with brake fluid.
b. Slowly open the bleeder valve 1/2 to 3/4 turn.
c. Have an assistant depress the brake pedal and hold until fluid begins to flow.
d. Close the bleeder valve and release the brake pedal. Repeat steps (b) through (d) until no air bubbles are present.
e. Relocate the bleeder hose on the forward hydraulic modulator bleeder valve and repeat steps (b) through (d). Inspect brake fluid level in reservoir and fill to the correct level if necessary. Make sure to replace the master cylinder reservoir cap.

NOTE: Once fluid is seen to flow from both hydraulic modulator bleeder valves, the hydraulic modulator is sufficiently full of brake fluid. However, it may not be completely purged of air. At this point, move to the wheel cylinders/calipers and bleed them. This ensures that the lowest points in the system are completely free of air and then the hydraulic modulator can be purged of any remaining air.

3. Raise and suitably support vehicle.
4. Bleed wheel cylinders/calipers in the sequence shown below.

Bleed Sequence: (1) Rear circuit (bleeder valve is at left rear wheel cylinder), (2) Right front, (3) Left front.

a. Attach a clear plastic bleeder hose to the bleeder valve on the wheel cylinder/caliper. Submerge the other end of the bleeder hose in a clean container partially filled with brake fluid.
b. Open the bleeder valve.
c. Have an assistant slowly depress the brake pedal.
d. Close the bleeder valve and release the brake pedal.
e. Wait five seconds.
f. Repeat steps (b) through (e) (including the five second waiting period) until the brake pedal feels firm and no air bubbles are observed in the bleeder hose.
g. Repeat steps (a) through (f) for the remaining wheels.
h. Tighten bleeder valve to 9 Nm (80 inch lbs.).
5. Lower vehicle.

NOTE: Inspect brake fluid level in reservoir and fill to the correct level if necessary. Make sure to replace the master cylinder reservoir cap.

6. Bleed hydraulic modulator:
a. Attach a clear plastic bleeder hose to the rearward bleeder valve on the hydraulic modulator. Submerge the other end of the bleeder hose in a clean container partially filled with brake fluid.
b. Have an assistant depress the brake pedal with moderate force.
c. Slowly open the bleeder valve 1/2 to 3/4 turn and allow fluid to flow.
d. Close bleeder valve and release brake pedal.
e. Wait five seconds.
f. Repeat steps B through E (including the five second waiting period) until all the air is purged from the system.
g. Relocate the bleeder hose on the forward hydraulic modulator bleeder valve and repeat steps B through F.
h. Tighten bleeder valve to 9 Nm (80 inch lbs.).
i. Inspect brake fluid level in reservoir and fill to the correct level if necessary. Make sure to replace the master cylinder reservoir cap.
7. With the ignition switch in ON, depress the brake pedal with moderate force and hold in position. Note pedal travel and feel.

NOTE: If pedal feels firm and constant and pedal travel is not excessive, perform following procedure:
a. Start the engine.
b. Carefully drive vehicle at 10 km/h (6 mph) for 5 seconds.
c. Stop vehicle.
d. Turn ignition switch to LOCK.
e. Repeat steps (a) through (d) one more time.
f. Re-check the pedal travel. If it is still firm and constant and pedal travel is not excessive, proceed with step 8.
g. If pedal feels soft or has excessive travel either initially or after engine start, using a Tech 2 scan tool, Release then apply the motors three times and cycle the solenoids 10 times. Be sure to apply the motors to ensure that the pistons are in the home position. DO NOT DRIVE THE VEHICLE. Repeat the entire bleeding procedure.

8. Road test the vehicle. Make several normal (non-ABS) stops from a moderate speed to ensure proper brake system function. Allow adequate cooling time between stops.