Rear brake problems
Thread Starter
Advanced
Joined: Nov 2012
Posts: 76
Likes: 28
From: Hayward CA
Rear brake problems
Hello fellow C8 members,
Just brought a used 2020 C8. The driver side rear brake squeals a lot when I come to a slow stop. It appears the rotors and pads are new. I greased the metal parts of the brake pad. Didn't help. I thought maybe there was air in the line, so I attempted to bleed the brakes. I started with the passenger side rear inside first. It blew a couple ounces of air out when I opened the line and then nothing. No fluid or nothing. I checked the other 3 lines and nothing came out. They are non Z51 Brembo brakes. I'm not an expert mechanic, but I can change brakes. I was reading about Brake Line Locking systems. Do you think that my rear brakes have been disabled with a line lock system? Oh, when I started the car after this, the brake failure light came on and there is a slight clicking noise when I press the brake petal, but the car seems to stop ok.
If it is a brake line lock, can it be remove and restored back to original?
Tony
Just brought a used 2020 C8. The driver side rear brake squeals a lot when I come to a slow stop. It appears the rotors and pads are new. I greased the metal parts of the brake pad. Didn't help. I thought maybe there was air in the line, so I attempted to bleed the brakes. I started with the passenger side rear inside first. It blew a couple ounces of air out when I opened the line and then nothing. No fluid or nothing. I checked the other 3 lines and nothing came out. They are non Z51 Brembo brakes. I'm not an expert mechanic, but I can change brakes. I was reading about Brake Line Locking systems. Do you think that my rear brakes have been disabled with a line lock system? Oh, when I started the car after this, the brake failure light came on and there is a slight clicking noise when I press the brake petal, but the car seems to stop ok.
If it is a brake line lock, can it be remove and restored back to original?
Tony
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At this point, I recommend you get it to a dealer to do a proper bleeding procedure:
Here's how the Shop Manual says to do it:
Here's how the Shop Manual says to do it:
Bleeding a Single Hydraulic Brake Circuit
1. Disconnect brake fluid level sensor
2. Use Global Diagnostic System (GDS) to deactivate brake boost system.
3. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
4. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
5. Note:
The pressure bleeding equipment must be the diaphragm type. The rubber diaphragm between the air supply and the brake fluid prevents
air, moisture, oil, and other contaminants from entering the hydraulic system.
6. Fill the brake master cylinder reservoir with GM approved brake fluid from a clean, sealed brake fluid container. Ensure that the brake
master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level. Brake
Master Cylinder Reservoir Filling
7. Check the brake fluid level in the CH-29532-A Pressure Brake Bleeder. Add GM approved brake fluid from a clean, sealed brake fluid
container as necessary to bring the level to approximately the half-full point. Adhesives, Fluids, Lubricants, and Sealers
8. Install the CH-44894-A Brake Bleeder Adapter to the brake master cylinder reservoir.
9. Connect the CH-29532-A Pressure Brake Bleeder, to the CH-44894-A Brake Bleeder Adapter.
10. Charge the CH-29532-A Pressure Brake Bleeder, air tank to 207kPa (30 psi).
11. Open the CH-29532-A Pressure Brake Bleeder, fluid tank valve to allow pressurized brake fluid to enter the brake system.
12. Wait approximately 30 seconds, then inspect the entire hydraulic brake system in order to ensure that there are no existing external
brake fluid leaks. Any brake fluid leaks identified require repair prior to completing this procedure. Brake System External Leak Inspection
13. Install a proper box-end wrench onto the wheel hydraulic circuit INNER bleeder valve which has been serviced.
14. Install a transparent hose over the end of the INNER bleeder valve.
15. 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. Adhesives, Fluids, Lubricants, and Sealers
16. Loosen the INNER bleeder valve to purge air from the wheel hydraulic circuit.
17. Allow fluid to flow until air bubbles stop flowing from the INNER bleeder.
18. Hand tighten the INNER bleeder valve.
19. Install a proper box-end wrench onto the wheel hydraulic circuit OUTER bleeder valve which has been serviced.
20. Install a transparent hose over the end of the OUTER bleeder valve.
21. 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. Adhesives, Fluids, Lubricants, and Sealers
22. Loosen the OUTER bleeder valve to purge air from the wheel hydraulic circuit.
23. Allow fluid to flow until air bubbles stop flowing from the OUTER bleeder.
24. After all air has been purged from the hydraulic circuit, tighten the bleeder valve to the necessary torque specification and install the dust
cap.
25.
Front Brake Caliper Bleeder Valve Replacement
Rear Brake Bleeder Valve Replacement
26. Note:
The brake reservoir may have residual pressure after the bleeding operation is complete. Wrap a clean shop towel around the bleeder
adapter and all hose connections before disconnecting the pressure bleeding equipment to prevent brake fluid from contacting and damaging
vehicle components and painted surfaces
27. Close the CH-29532-A Pressure Brake Bleeder, fluid tank valve, then disconnect the CH-29532-A Pressure Brake Bleeder, from the
CH-44894-A Brake Bleeder Adapter.
28. Remove the CH-44894-A Brake Bleeder Adapter from the brake master cylinder reservoir.
29. Fill the brake master cylinder reservoir to the maximum-fill level with GM approved brake fluid from a clean, sealed brake fluid container.
Adhesives, Fluids, Lubricants, and Sealers
30. Inspect the brake system for external leaks. Brake System External Leak Inspection
31. Run the GDS - Brake Hydraulic Test, if it fails, perform the Bleeding the Complete Brake Hydraulic System procedure.
32. Connect the brake fluid level sensor
33. Turn the ignition ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.
34. Inspect the brake system for external leaks. Brake System External Leak Inspection
35. Note:
DO NOT allow the vehicle to be driven until it is diagnosed and repaired.
36. If the brake system warning lamp remains illuminated, go to Diagnostic Starting Point - Vehicle.
1. Disconnect brake fluid level sensor
2. Use Global Diagnostic System (GDS) to deactivate brake boost system.
3. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
4. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
5. Note:
The pressure bleeding equipment must be the diaphragm type. The rubber diaphragm between the air supply and the brake fluid prevents
air, moisture, oil, and other contaminants from entering the hydraulic system.
6. Fill the brake master cylinder reservoir with GM approved brake fluid from a clean, sealed brake fluid container. Ensure that the brake
master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level. Brake
Master Cylinder Reservoir Filling
7. Check the brake fluid level in the CH-29532-A Pressure Brake Bleeder. Add GM approved brake fluid from a clean, sealed brake fluid
container as necessary to bring the level to approximately the half-full point. Adhesives, Fluids, Lubricants, and Sealers
8. Install the CH-44894-A Brake Bleeder Adapter to the brake master cylinder reservoir.
9. Connect the CH-29532-A Pressure Brake Bleeder, to the CH-44894-A Brake Bleeder Adapter.
10. Charge the CH-29532-A Pressure Brake Bleeder, air tank to 207kPa (30 psi).
11. Open the CH-29532-A Pressure Brake Bleeder, fluid tank valve to allow pressurized brake fluid to enter the brake system.
12. Wait approximately 30 seconds, then inspect the entire hydraulic brake system in order to ensure that there are no existing external
brake fluid leaks. Any brake fluid leaks identified require repair prior to completing this procedure. Brake System External Leak Inspection
13. Install a proper box-end wrench onto the wheel hydraulic circuit INNER bleeder valve which has been serviced.
14. Install a transparent hose over the end of the INNER bleeder valve.
15. 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. Adhesives, Fluids, Lubricants, and Sealers
16. Loosen the INNER bleeder valve to purge air from the wheel hydraulic circuit.
17. Allow fluid to flow until air bubbles stop flowing from the INNER bleeder.
18. Hand tighten the INNER bleeder valve.
19. Install a proper box-end wrench onto the wheel hydraulic circuit OUTER bleeder valve which has been serviced.
20. Install a transparent hose over the end of the OUTER bleeder valve.
21. 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. Adhesives, Fluids, Lubricants, and Sealers
22. Loosen the OUTER bleeder valve to purge air from the wheel hydraulic circuit.
23. Allow fluid to flow until air bubbles stop flowing from the OUTER bleeder.
24. After all air has been purged from the hydraulic circuit, tighten the bleeder valve to the necessary torque specification and install the dust
cap.
25.
Front Brake Caliper Bleeder Valve Replacement
Rear Brake Bleeder Valve Replacement
26. Note:
The brake reservoir may have residual pressure after the bleeding operation is complete. Wrap a clean shop towel around the bleeder
adapter and all hose connections before disconnecting the pressure bleeding equipment to prevent brake fluid from contacting and damaging
vehicle components and painted surfaces
27. Close the CH-29532-A Pressure Brake Bleeder, fluid tank valve, then disconnect the CH-29532-A Pressure Brake Bleeder, from the
CH-44894-A Brake Bleeder Adapter.
28. Remove the CH-44894-A Brake Bleeder Adapter from the brake master cylinder reservoir.
29. Fill the brake master cylinder reservoir to the maximum-fill level with GM approved brake fluid from a clean, sealed brake fluid container.
Adhesives, Fluids, Lubricants, and Sealers
30. Inspect the brake system for external leaks. Brake System External Leak Inspection
31. Run the GDS - Brake Hydraulic Test, if it fails, perform the Bleeding the Complete Brake Hydraulic System procedure.
32. Connect the brake fluid level sensor
33. Turn the ignition ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.
34. Inspect the brake system for external leaks. Brake System External Leak Inspection
35. Note:
DO NOT allow the vehicle to be driven until it is diagnosed and repaired.
36. If the brake system warning lamp remains illuminated, go to Diagnostic Starting Point - Vehicle.
Thread Starter
Advanced
Joined: Nov 2012
Posts: 76
Likes: 28
From: Hayward CA
Please disregard. After a little research, I found that with the electronic brake system, you have to disconnect the battery prior to any work, otherwise if the car does a self check at anytime you're messing with it, it will fail the pressurization test and cause a fault (brake failure fault). There's a procedure to force the system to test itself and correct this fault assuming there are no real problems.
Thanks for the advice and sorry for taking up your time.
Tony
Thanks for the advice and sorry for taking up your time.
Tony
