Manual

Bleeding is necessary if air has entered the hydraulic brake system. It may be necessary to bleed the system at all four wheels if a low fluid level allowed air to enter the system, or the brake pipes have been disconnected at the master cylinder or combination valve. If a pipe is disconnected at one wheel, then only bleed that wheel.

The time required to bleed the hydraulic system when the master cylinder is removed can be reduced by bleeding the master cylinder before installing it on the vehicle.

If the Brake Pressure Modulator Valve (BPMV) has been replaced or has air trapped in it, refer Antilock Brake System, BPMV. Service and Repair

Manual Bleeding (Recommended Method)

CAUTION: Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills.

^ Relieve the pressure reserve by applying the brakes several times with the ignition "OFF."

1. Fill the master cylinder reservoirs with Delco Supreme 11 Hydraulic Brake Fluid GM P/N 1052535 or an equivalent DOT 3 motor vehicle brake fluid.

^ Maintain the fluid level during bleeding.

2. If the master cylinder is replaced or suspected to have air in the bore, bleed it before any wheel cylinder or caliper.
a. Disconnect the forward brake pipe connection at the master cylinder.
b. Allow the brake fluid to flow from the connector port.
c. Connect the brake pipe but do not tighten loose fitting.
d. Tighten the fitting before releasing the pedal.
e. Wait 15 seconds.
f. Repeat this sequence, including the 15-second wait, until all air is purged from the bore.
g. After all air has been removed from the forward connection, repeat this procedure for the rear pipe.
3. If the BPMV of the Four Wheel Antilock (4WAL) system is replaced or suspected to have air trapped inside, it must be bled next. Refer to Antilock Brake System, BPMV.
4. Bleed each wheel in the following sequence:
A. Right rear
B. Left rear
C. Right front
D. Left front
5 Attach a hose to the wheel cylinder/caliper bleeder valve.

^ Immerse the opposite end of the hose into a container partially filled with clean brake fluid.

6. Loosen the bleeder valve 1/2 to 1 turn.
7. Slowly apply the brake pedal to full travel one time and hold.
8. Tighten the bleeder valve and slowly release the pedal.
9. Wait 15 seconds. Check the master cylinder fluid level.
10. Repeat this sequence, including the 15-second wait, until one pint of fluid has been bled and no air is seen in the fluid.
11. Tighten the bleeder valve to 7 Nm (62 inch lbs.).
12. Repeat steps 5 through 11 at each wheel until the system is bled.
13. Use a Scan Tool to perform four 4WAL function tests.
14. Re-bleed each wheel circuit.
15. Check the brake pedal for "sponginess" and the brake warning lamp. Repeat the bleeding procedure to correct either of these conditions.