Chevrolet Cobalt Service & Repair Manual: Brake System Bleed

Chevrolet Cobalt Service & Repair Manual / Brakes / Hydraulic Brake Systems / Brake System Bleed

Brake fluid is corrosive to painted surfaces. Care must be taken not to allow brake fluid to come in contact with painted surfaces on vehicle.
When bleeding the brake system, always bleed righthand rear wheel circuit first, followed by the lefthand front, lefthand rear and, finally, righthand front.

Manual

Pressure bleeding is recommended for all hydraulic systems. However, if a pressure bleeder is unavailable, use the following procedure. Brake fluid damages painted surfaces. Immediately clean any spilled fluid.
1. Remove vacuum reserve by pumping brakes several times with engine off.
2. Fill master cylinder reservoir with clean brake fluid. Do not let reservoir fall below half full during bleeding procedure.
3. If required, bleed master cylinder as follows:
  a. Loosen master cylinder forward brake line connection until fluid flows from reservoir, then tighten brake line.
  b. Have assistant to slowly depress brake pedal one time and hold.
  c. Loosen front brake line connection and purge air from cylinder.
  d. Tighten connection and slowly release brake pedal.
  e. Wait 15 seconds, then repeat previous steps until all air is purged.
  f. Bleed rearward brake line connection by repeating previous steps.
4. Loosen and tighten bleeder valves at all four wheels.
5. Bleed calipers or wheel cylinders in sequence outlined in "Bleed Sequence."
6. Place one end of transparent tube over bleeder valve and submerge other end into transparent container filled with clean brake fluid.
7. Have assistant slowly depress brake pedal one time and hold.
8. Loosen bleeder valve and purge air from wheel cylinder or caliper. Tighten bleeder screw and slowly release pedal.
9. Wait 15 seconds and repeat previous steps until all air is bled from system.

Pressure

1. Loosen and tighten bleeder valves at all four wheels.
2. Install suitable bleeder adapter to master cylinder using diaphragm type pressure bleeder.
3. Charge bleeder ball to 20-25 psi.
4. Connect pressure bleeder line to adapter.
5. Open line valve on pressure bleeder and depress bleed-off valve on adapter until small amount of brake fluid is released.
6. Raise and support vehicle.
7. Bleed calipers or wheel cylinders in sequence as outlined in "Bleed Sequence."
8. Place one end of transparent tube over bleeder valve and submerge other end into transparent container filled with clean brake fluid.
9. Open bleeder valve approximately, 3/4 turn and allow fluid to flow into container until all air is purged from line.

Bleed Sequence

On models equipped with front and rear split system, righthand rear, lefthand rear, righthand front, lefthand front. If pressure bleeding, bleed front brakes together and rear brakes together.
On models equipped with diagonally split system,righthand rear, lefthand front, lefthand rear, righthand front.
    Hydraulic Brake Systems
    ...

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