Manual Bleeding

BLEEDING BRAKE HYDRAULIC SYSTEM

CAUTION: Do not move the vehicle until a firm brake pedal is obtained. Air in the brake system can cause loss of brakes with possible personal injury.

Whenever air gets into the brake hydraulic system, you must bleed the system to remove it. You might have to bleed the hydraulic system at all four wheel positions if air has entered the system due to low fluid level, or from brake pipes having been disconnected at the master cylinder. If a brake pipe is disconnected at one wheel, only that wheel cylinder/caliper needs to be bled. if pipes are disconnected at any fitting located between the master cylinder and the wheels, then the brake system served by the disconnected pipe must be bled.

MANUAL BLEEDING

Fig. 1 Wheel Cylinder Bleeding:

TOOLS REQUIRED:
^ J 21472 Bleeder Wrench
^ J 28434 Bleeder Wrench

Deplete the booster reserve by applying the brakes several times with the engine off until all reserve is depleted.
Be very careful to prevent brake fluid from getting on painted surfaces.

ADJUST
1. Fill master cylinder reservoir to full level mark using only Delco Supreme II Brake Fluid, or equivalent DOT-3 brake fluid.
^ Maintain fluid level in reservoir during bleeding.
^ Have an assistant press the brake pedal, when needed, during bleeding.

IMPORTANT: Be sure the master cylinder reservoir cap is installed before the brake pedal is pressed. This prevents brake fluid from spraying from the reservoir.

2. If master cylinder is known or suspected to have air in the bore, bleed it as follows before bleeding any wheel cylinder or caliper.
a. Loosen forward brake pipe connection at the master cylinder.
b. Allow brake fluid to flow from connector port. Maintain reservoir fluid level.
c. Tighten forward brake pipe on master cylinder.
d. Depress brake pedal slowly one time and hold. Loosen forward brake pipe connection again to purge air from the bore. Tighten the connection and then slowly release the brake pedal. Wait 15 seconds. Repeat the sequence, including the 15 second wait, until all air is removed from the bore.

TIGHTEN
^ Brake pipe connection to 15 Nm (11 lb. ft.).

e. Repeat Step 2 and bleed the master cylinder at the rear connection.
3. Bleed individual wheel calipers/cylinders only after all air is removed from the master cylinder. If you know the calipers/cylinders do not contain air, then you do not have to bleed them.
4. If you must bleed all the wheel circuits, use the following sequence: Right rear, left rear, right front, and then left front.
5. Raise vehicle and suitably support.
6. Remove bleeder valve cap and place proper size box-end wrench, or J 21472 / J 28434, over bleeder valve.
7. Attach a transparent tube to bleeder valve, submerge other end of tube in a clear container, partially filled with clean brake fluid.
8. Depress brake pedal slowly one time and hold. Use slow pedal action. Rapid pedal pumping pushes the master cylinder secondary piston down the bore in a way that makes it difficult to bleed the system.
a. Loosen bleeder valve to purge air from the caliper/cylinder.
b. Tighten bleeder valve, and slowly release brake pedal.
c. Wait 15 seconds, then repeat the sequence, including the 15 second wait, until all air is removed. You might have to repeat the sequence 10 or more times to remove all the air.

TIGHTEN
^ Wheel cylinder bleeder valve to 10 Nm (88 lb. in.).
^ Caliper bleeder valve to 13 Nm (115 lb. in.).

9. Install bleeder valve caps.
10. Lower vehicle.
11. Fill master cylinder to full mark.
12. Check brake pedal for "sponginess". Repeat entire bleeding procedure to correct "sponginess".