Chevrolet Sonic Repair Manual: Hydraulic Brake System Bleeding (Manual)

If hydraulic components were serviced on only one wheel hydraulic circuit, perform the following procedure.

1. With the ignition OFF and the brakes cool, apply the brakes 3–5 times, or until the brake pedal effort increases significantly, in order to deplete the brake booster power reserve.
2. Place a clean shop cloth beneath the brake master cylinder to catch brake fluid spills.
3. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
4. Fill the brake master cylinder reservoir to the maximum-full level with GM approved brake fluid from a clean, sealed brake fluid container. Add brake fluid as needed to ensure that the brake master cylinder reservoir remains at least half-full throughout the bleed procedure. The reservoir cap must be installed at all times except when filling the reservoir. Refer to Fluid and Lubricant Recommendations.
5. Install a proper box-end wrench onto the wheel hydraulic circuit bleeder valve which has been serviced.
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 brake fluid from a clean, sealed brake fluid container.
8. Have an assistant slowly press the brake pedal fully and maintain steady pressure on the 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, then repeat steps 8-10 until all air is purged from the wheel hydraulic circuit.
12. After all air has been purged from the hydraulic circuit, tighten the bleeder valve and install the dust cap.
13. Fill the brake master cylinder reservoir to the maximum-fill level with GM approved brake fluid from a clean, sealed brake fluid container.
14. Slowly press and release the brake pedal. Observe the brake pedal feel.
15. If the brake pedal feels spongy, perform the Bleeding the Complete Brake Hydraulic System procedure:
16. Turn the ignition key 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.

17. If the brake system warning lamp remains illuminated, refer to Diagnostic Starting Point - Vehicle.

1. With the ignition OFF and the brakes cool, apply the brakes 3–5 times, or until the brake pedal effort increases significantly, in order to deplete the brake booster power reserve.
2. Place a clean shop cloth beneath the brake master cylinder to catch brake fluid spills.
3. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
4. Fill the brake master cylinder reservoir to the maximum-full level with GM approved brake fluid from a clean, sealed brake fluid container. Add brake fluid as needed to ensure that the brake master cylinder reservoir remains at least half-full throughout the bleed procedure. The reservoir cap must be installed at all times except when filling the reservoir. Refer to Fluid and Lubricant Recommendations.
5. If the master cylinder was replaced, the master cylinder must be bench bled. Refer to Master Cylinder Bench Bleeding.
6. If the brake pipes have been removed from the master cylinder, the following steps must be performed.
1. With the rear brake pipe installed securely to the master cylinder, loosen and separate the front brake pipe fitting from the front port of the brake master cylinder.
2. Allow a small amount of brake fluid to gravity bleed from the open port of the master cylinder. Capture and properly dispose of the brake fluid in an approved container.
3. Install the front brake pipe fitting to the front port of the brake master cylinder and tighten the fitting. Refer to Fastener Tightening Specifications.
4. Have an assistant slowly press the brake pedal fully and maintain steady pressure on the pedal.
5. Loosen the front brake pipe fitting from the front port of the brake master cylinder to purge air from the master cylinder port.
6. Tighten the front brake pipe fitting, then have the assistant slowly release the brake pedal.
7. Wait 15 seconds, then repeat steps 6.4-6.6 until all air is purged from the front brake pipe fitting of the front port of the master cylinder.
8. After all air is purged from the front port of the brake master cylinder, tighten the front master cylinder brake pipe fitting. Refer to Fastener Tightening Specifications.
9. With the front brake pipe fitting installed securely to the front port of the brake master cylinder, loosen and separate the rear brake pipe fitting from the rear port of the brake master cylinder.
10. Repeat steps 6.2-6.7 for the rear port of the brake master cylinder.
11. After all air is purged from the rear port of the brake master cylinder, tighten the rear master cylinder brake pipe fitting. Refer to Fastener Tightening Specifications.
12. Slowly press and release the brake pedal. Observe the brake pedal feel.
13. If the brake pedal feels spongy, proceed to step 7.
14. If the brake pedal feels firm, proceed to step 24.
7. If the brake pipes have been removed from the brake pressure modulator valve (BPMV) assembly, if equipped, or the brake proportion valve assembly, if equipped, air must be purged from each port of the respective assembly beginning with the feed pipes from the master cylinder.
1. Loosen and separate one of the master cylinder brake pipe fittings from the inlet port of the assembly to be bled.
2. Allow a small amount of brake fluid to gravity bleed from the open port of the assembly. Capture and properly dispose of the brake fluid in an approved container.
3. Install the brake pipe fitting and to the inlet port of the assembly and tighten securely.
4. Have an assistant slowly press the brake pedal fully and maintain steady pressure on the pedal.
5. Loosen the same brake pipe fitting to purge air from the open port of the assembly.
6. Tighten the brake pipe fitting, then have the assistant slowly release the brake pedal.
7. Wait 15 seconds, then repeat steps 7.4-7.6 until all air is purged from the brake pipe fitting of the assembly.
8. Repeat steps 7.1-7.7 for all of the remaining ports of the assembly.
9. After bleeding each port of the assembly, tighten all of the brake pipe fittings on the assembly. Refer to Fastener Tightening Specifications.
10. Fill the master cylinder reservoir to the maximum-full level with GM approved brake fluid from a clean, sealed brake fluid container.
11. Slowly press and release the brake pedal. Observe the brake pedal feel.
12. If the brake pedal feels spongy, proceed to step 8.
13. If the brake pedal feels firm, proceed to step 24.
8. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
9. Install a transparent hose over the end of the bleeder valve.
10. Submerge the open end of the transparent hose into a transparent container partially filled with GM approved brake fluid from a clean, sealed brake fluid container.
11. Have an assistant slowly press the brake pedal fully and maintain steady pressure on the brake pedal.
12. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
13. Tighten the bleeder valve, then have the assistant slowly release the brake pedal.
14. Wait 15 seconds, then repeat steps 11-13 until all air is purged from the wheel hydraulic circuit.
15. Tighten the RIGHT REAR hydraulic wheel circuit bleeder valve securely.
16. Install a proper box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve, then repeat steps 9-14..
17. Install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve, then repeat steps 9-14..
18. Install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit bleeder valve, then repeat steps 9-14..
19. After completing the final wheel hydraulic circuit bleeding procedure, tighten all of the wheel hydraulic circuit bleeder valves and install the bleeder valve dust caps.
20. Fill the master cylinder reservoir to the maximum-full level with GM approved brake fluid from a clean, sealed brake fluid container.
21. Slowly press and release the brake pedal. Observe the brake pedal feel.
22. If the brake pedal feels spongy, perform the following procedure.
1. If equipped with antilock brakes, install a scan tool and perform the Antilock Brake System Automated Bleed to remove air which may be trapped in the BPMV.
2. Inspect the hydraulic brake system for external leaks. Refer to Brake System External Leak Inspection.
3. Repeat the Bleeding the Complete Brake Hydraulic System procedure.
23. If the brake pedal still feels spongy, pressure bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding
24. Turn the ignition switch 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 the brake system is diagnosed and repaired.

25. If the brake system warning lamp remains illuminated, refer to Diagnostic Starting Point - Vehicle.

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