For 1990-2009 cars

## Hydraulic Brake System Bleeding Manual

Warning: Refer to Brake Fluid Irritant Warning in the Preface section.

Caution: Refer to Brake Fluid Effects on Paint and Electrical Components Caution in the Preface section.

1. Place a clean shop cloth beneath the brake master cylinder reservoir to catch brake fluid spills.
2. With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal effort increases significantly, to deplete the brake booster power reserve.
3. If you have performed a master cylinder bench bleeding on this vehicle, or if you have disconnected the brake pipes from the proportioning valve assembly or the brake modulator assembly, you must perform the following steps to bleed air at the ports of the hydraulic component.

3.1. | Fill the master cylinder reservoir (combined with the hydraulic clutch (on manual (transmission) to the maximum-full level with GM approved or equivalent brake fluid from a clean, sealed brake fluid container.

If removal of the reservoir cap and diaphragm is necessary, clean the outside of the reservoir on and around the cap prior to removal.

3.2. | With the brake pipes installed securely to the master cylinder, proportioning valve assembly, or the brake modulator assembly, loosen and separate one of the brake pipes from the port of the component.

| Note: For the proportioning valve assembly or the brake modulator assembly, perform these steps in the sequence of system flow; begin with the fluid feed pipes on the master cylinder.

3.3. | Allow a small amount of brake fluid to gravity bleed from the open port of the component.

3.4. | Connect the brake pipe fitting to the component and tighten securely.

3.5. | Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the brake pedal.

3.6. | Loosen the same brake pipe fitting to purge air from the open port of the component.

3.7. | Tighten the brake pipe fitting, then have the assistant slowly release the brake pedal.

3.8. | Wait 15 seconds, then repeat steps 3.3-3.7 until all air is purged from the same port of the component.

3.9. | With the brake pipe fitting installed securely to the master cylinder, proportioning valve assembly, or brake modulator assembly after all air been purged from the first port of the component that was bled, loosen and separate the next brake pipe from the component and repeat steps 3.3-3.8 until each of the ports on the component has been bled.

3.10. | After completing the final component bleeding procedure, ensure each of the brake pipe fittings is properly tightened.

4. Fill the master cylinder reservoir and combined hydraulic clutch, if equipped, to the maximum-full level with GM approved or equivalent brake fluid from a clean, sealed brake fluid container. Ensure the master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level.

Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.

5. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
6. Install a transparent hose over the end of the bleeder valve.
7. Submerge the open end of the transparent hose into a transparent container partially filled with GM approved or equivalent brake fluid from a clean, sealed brake fluid container.
8. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the brake pedal.
9. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
10. Tighten the bleeder valve, then have the assistant slowly release the brake pedal.
11. Wait 15 seconds, the repeat steps 8-10 until all air is purged from the same wheel hydraulic circuit.
12. With the right rear wheel hydraulic circuit bleeder valve tightened securely and after all air has been purged from the right rear wheel hydraulic circuit, install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit bleeder valve.
13. For Cobalt SS, install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit INBOARD bleeder valve.
14. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
15. For Cobalt SS, install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit, OUTBOARD bleeder valve.
16. For Cobalt SS, install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
17. With the left front wheel hydraulic circuit bleeder valve tightened securely and after all air has been purged from the left front wheel hydraulic circuit, install a proper box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve.
18. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
19. With the left rear wheel hydraulic circuit bleeder valve tightened securely and after all air has been purged from the left rear wheel hydraulic circuit, install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve.
20. For Cobalt SS, install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit INBOARD bleeder valve.
21. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
22. For Cobalt SS, install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit, OUTBOARD bleeder valve.
23. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
24. After completing the final wheel hydraulic circuit bleeding procedure, ensure each of the 4 wheel hydraulic circuit bleeder valves is properly tightened.
25. For Cobalt SS, after completing the final wheel hydraulic circuit bleeding procedure, ensure each of the 6 wheel hydraulic circuit bleeder valves is properly tightened.
26. Fill the brake master cylinder reservoir to the maximum-full level with GM approved or equivalent brake fluid from a clean, sealed brake fluid container.
27. Slowly depress and release the brake pedal. Observe the brake pedal feel.
28. If the brake pedal feels spongy, repeat the bleeding procedure. If the brake pedal stills feels spongy after repeating the bleeding procedure, perform the following steps:

28.1. | Inspect the brake system for external leaks. Refer to Brake System External Leak Inspection.

28.2. | Pressure bleed the hydraulic brake system in order to purge any air which may still be trapped in the system.

29. Turn the ignition ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.

Note: DO NOT allow the vehicle to be driven until it is diagnosed and repaired.

30. If the brake system warning lamp remains illuminated, refer to Symptoms - Hydraulic Brakes.

## Hydraulic Brake System Bleeding Pressure

#### Special Tools

• | J-29532 Diaphragm Type Brake Pressure Bleeder, or equivalent

• | J-44894-A Brake Pressure Bleeder Adapter

Warning: Refer to Brake Fluid Irritant Warning in the Preface section.

Caution: Refer to Brake Fluid Effects on Paint and Electrical Components Caution in the Preface section.

1. Place a clean shop cloth beneath the brake master cylinder reservoir to catch brake fluid spills.
2. With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal effort increases significantly, to deplete the brake booster power reserve.
3. If you have performed a master cylinder bench bleeding on this vehicle, or if you have disconnected the brake pipes from the proportioning valve assembly or the brake modulator assembly, you must perform the following steps to bleed air at the ports of the hydraulic component.

3.1. | Fill the master cylinder reservoir (combined with the hydraulic clutch (on manual (transmission) to the maximum-full level with GM approved or equivalent brake fluid from a clean, sealed brake fluid container.

If removal of the reservoir cap and diaphragm is necessary, clean the outside of the reservoir on and around the cap prior to removal.

3.2. | With the brake pipes installed securely to the master cylinder, proportioning valve assembly, or the brake modulator assembly, loosen and separate one of the brake pipes from the port of the component.

| Note: For the proportioning valve assembly or the brake modulator assembly, perform these steps in the sequence of system flow; begin with the fluid feed pipes on the master cylinder.

3.3. | Allow a small amount of brake fluid to gravity bleed from the open port of the component.

3.4. | Connect the brake pipe fitting to the component and tighten securely.

3.5. | Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the brake pedal.

3.6. | Loosen the same brake pipe fitting to purge air from the open port of the component.

3.7. | Tighten the brake pipe fitting, then have the assistant slowly release the brake pedal.

3.8. | Wait 15 seconds, then repeat steps 3.3-3.7 until all air is purged from the same port of the component.

3.9. | With the brake pipe fitting installed securely to the master cylinder, proportioning valve assembly, or brake modulator assembly after all air been purged from the first port of the component that was bled, loosen and separate the next brake pipe from the component and repeat steps 3.3-3.8 until each of the ports on the component has been bled.

3.10. | After completing the final component bleeding procedure, ensure each of the brake pipe fittings is properly tightened.

4. Fill the master cylinder reservoir and combined hydraulic clutch, if equipped, to the maximum-full level with GM approved or equivalent brake fluid from a clean, sealed brake fluid container. Ensure the master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level.

Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.

5. 5. Install the J-44894-A Brake Pressure Bleeder Adapter to the brake master cylinder reservoir.
6. 6. Check the brake fluid level in the J-29532 Diaphragm Type Brake Pressure Bleeder, or equivalent . Add GM approved or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container as necessary to bring the level to approximately the half-full point.
7. 7. Connect the J-29532 Diaphragm Type Brake Pressure Bleeder, or equivalent , to the J-44894-A Brake Pressure Bleeder Adapter .
8. 8. Charge the J-29532 Diaphragm Type Brake Pressure Bleeder, or equivalent , air tank to 175-205 kPa (25-30 psi).
9. 9. Open the J-29532 Diaphragm Type Brake Pressure Bleeder, or equivalent , fluid tank valve to allow pressurized brake fluid to enter the brake system.
10. 10. Wait approximately 30 seconds, and then inspect the entire hydraulic brake system in order to ensure there are no existing external brake fluid leaks.

Any brake fluid leaks identified require repair prior to completing this procedure.

11. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
12. Install a transparent hose over the end of the bleeder valve.
13. Submerge the open end of the transparent hose into a transparent container partially filled with GM approved or equivalent brake fluid from a clean, sealed brake fluid container.
14. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
15. When air bubbles no longer appear from the bleeder, tighten the bleeder valve.
16. With the right rear wheel hydraulic circuit bleeder valve tightened securely and after all air has been purged from the right rear wheel hydraulic circuit, install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit bleeder valve.
17. For Cobalt SS, install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit INBOARD bleeder valve.
18. Install a transparent hose over the end of the bleeder valve, then repeat steps 13-15.
19. For Cobalt SS, install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit, OUTBOARD bleeder valve.
20. For Cobalt SS, install a transparent hose over the end of the bleeder valve, then repeat steps 13-15.
21. With the left front wheel hydraulic circuit bleeder valve tightened securely and after all air has been purged from the left front wheel hydraulic circuit, install a proper box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve.
22. Install a transparent hose over the end of the bleeder valve, then repeat steps 13-15.
23. With the left rear wheel hydraulic circuit bleeder valve tightened securely and after all air has been purged from the left rear wheel hydraulic circuit, install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve.
24. For Cobalt SS, install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit INBOARD bleeder valve.
25. Install a transparent hose over the end of the bleeder valve, then repeat steps 13-15.
26. For Cobalt SS, install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit, OUTBOARD bleeder valve.
27. Install a transparent hose over the end of the bleeder valve, then repeat steps 13-15.
28. After completing the final wheel hydraulic circuit bleeding procedure, ensure each of the 4 wheel hydraulic circuit bleeder valves is properly tightened.
29. For Cobalt SS, after completing the final wheel hydraulic circuit bleeding procedure, ensure each of the 6 wheel hydraulic circuit bleeder valves is properly tightened.
30. Close the J-29532 Diaphragm Type Brake Pressure Bleeder, or equivalent , fluid tank valve, and then disconnect the J-29532 Diaphragm Type Brake Pressure Bleeder, or equivalent , from the J-44894-A Brake Pressure Bleeder Adapter .
31. 31. Remove the J-44894-A Brake Pressure Bleeder Adapter from the brake master cylinder reservoir.
32. Fill the brake master cylinder reservoir to the maximum-full level with GM approved or equivalent brake fluid from a clean, sealed brake fluid container.
33. Slowly depress and release the brake pedal. Observe the brake pedal feel.
34. If the brake pedal feels spongy, repeat the bleeding procedure. If the brake pedal stills feels spongy after repeating the bleeding procedure, perform the following steps:

34.1. | Inspect the brake system for external leaks. Refer to Brake System External Leak Inspection.

34.2. | If equipped with antilock brakes, using a scan tool, perform the antilock brake system automated bleeding procedure to remove any air that may have been trapped in the brake pressure modulator valve (BPMV). Refer to Antilock Brake System Automated Bleed Procedure.

35. Turn the ignition ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.

Note: DO NOT allow the vehicle to be driven until it is diagnosed and repaired.

36. If the brake system warning lamp remains illuminated, refer to Symptoms - Hydraulic Brakes.

## Hydraulic Brake System Bleeding Rear Brake Caliper - Cobalt SS

#### Special Tools

• | J-29532 Diaphragm Type Pressure Bleeder, or equivalent

• | J-44894-A Brake Pressure Bleeder Adapter

Warning: Refer to Brake Fluid Irritant Warning in the Preface section.

Caution: Refer to Brake Fluid Effects on Paint and Electrical Components Caution in the Preface section.

1. Place a clean shop cloth beneath the brake master cylinder to catch any brake fluid spills.
2. With the ignition OFF and the brakes cool, apply the brake pedal 3-5 times, or until the brake pedal becomes firm, to deplete the brake booster vacuum reserve.
3. Fill the brake master cylinder reservoir and combined hydraulic clutch, if equipped, to the maximum-full level with GM approved or equivalent brake fluid from a clean sealed brake fluid container.

Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.

4. Install the J-44894-A Brake Pressure Bleeder Adapter to the brake master cylinder reservoir.
5. Check the brake fluid level in the J-29532 Diaphragm Type Pressure Bleeder, or equivalent . Add GM approved or equivalent brake fluid from a clean, sealed brake fluid container as necessary to bring the level to approximately the half-full point.
6. Connect the J-29532 Diaphragm Type Pressure Bleeder, or equivalent to the J-44894-A Brake Pressure Bleeder Adapter .
7. Charge the J-29532 Diaphragm Type Pressure Bleeder, or equivalent , air tank to 175-205 kPa (25-30 psi).
8. Open the J-29532 Diaphragm Type Pressure Bleeder, or equivalent , fluid tank valve to allow pressurized brake fluid to enter the brake system.
9. Wait approximately 30 seconds, then inspect the entire hydraulic brake system to ensure there are no existing brake fluid leaks.

Any brake fluid leaks identified require repair prior to completing this procedure.

10. Without disconnecting the brake caliper hose and without removing the rear disc brake pads, remove the rear brake caliper from the caliper bracket. Refer to Rear Brake Caliper Replacement.
11. Using a spanner type caliper piston retractor tool, extend the brake caliper piston as far as possible without disengaging the brake caliper piston.
12. Install a proper box-end wrench onto the brake caliper bleeder valve.
13. Install a transparent hose over the end of the bleeder valve.
14. Submerge the open end of the transparent hose into a transparent container partially filled with GM approved or equivalent brake fluid from a clean, sealed brake fluid container.
15. Invert the rear brake caliper and position the bleeder valve vertically.
16. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
17. Using a rubber or plastic faced mallet, tap the brake caliper housing in various locations near the bleeder valve.
18. While tapping the brake caliper housing, allow brake fluid to flow until air bubbles no longer appear from the bleeder valve.
19. Tighten the bleeder valve. Refer to Fastener Tightening Specifications.
20. Inspect the J-29532 Diaphragm Type Pressure Bleeder, or equivalent state of charge. Following the brake bleeder manufacturer instructions, charge the air tank to 175-205 kPa (25-30 psi), if necessary.
21. Install a spanner type brake caliper piston retractor tool to the brake caliper piston.
22. Loosen the bleeder valve.
23. Using a rubber or plastic faced mallet, tap the brake caliper housing in various locations near the bleeder valve.
24. Using the spanner type brake caliper piston retractor tool, slowly retract the brake caliper piston.
25. Continue to observe the brake fluid flow from the bleeder valve through the transparent bleeder hose.
26. When the brake caliper piston is fully retracted, tap the brake caliper housing using a rubber or plastic faced mallet in various locations near the bleeder valve.
27. While tapping on the brake caliper housing, allow brake fluid to flow until air bubbles no longer appear from the bleeder valve.
28. Tighten the bleeder valve.
29. Install the rear disc brake caliper. Refer to Rear Brake Caliper Replacement.
30. If necessary, repeat steps 10-29 for the opposite rear disc brake caliper.
31. Close the J-29532 Diaphragm Type Pressure Bleeder, or equivalent fluid tank valve, and disconnect the J-29532 Diaphragm Type Pressure Bleeder, or equivalent from the J-44894-A Brake Pressure Bleeder Adapter .
32. Remove the J-44894-A Brake Pressure Bleeder Adapter from the master cylinder reservoir.
33. Fill the brake master cylinder reservoir to the maximum-full level with GM approved or equivalent brake fluid from a clean, sealed brake fluid container.
34. Slowly press and release the brake pedal. Observe the brake pedal feel.
35. If the brake pedal feels spongy, perform the following steps:

35.1. | Inspect the brake system for external leaks. Refer to Brake System External Leak Inspection.

35.2. | Using a scan tool, perform antilock brake system automated bleed procedure to remove any air that may have been trapped in the brake pressure modulator valve. Refer to Antilock Brake System Automated Bleed Procedure.

36. Turn the ignition ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.

Note: DO NOT allow the vehicle to be driven until it is diagnosed and repaired.

37. If the brake system lamp remains illuminated, refer to Symptoms - Hydraulic Brakes.