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HOMESERVICE MANUALSOLDSMOBILE2004BRAVADA AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 50 (DISC BRAKES)SYSTEM TESTSHYDRAULIC BRAKE SYSTEM TESTING
2004 Oldsmobile Bravada AWD

Hydraulic Brake System Testing

2004 Oldsmobile Bravada AWDSECTION Hydraulic Brake System Testing
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
  1. Were you sent here from DIAGNOSTIC STARTING POINT - HYDRAULIC BRAKES? If so, go to next step. If not, go to DIAGNOSTIC STARTING POINT - HYDRAULIC BRAKES  under TROUBLE SHOOTING.
  2. Inspect and adjust (if necessary) the brake fluid level in the brake master cylinder. Was the brake fluid level low? If so, go to next step. If not, go to step  4 .
  3. Inspect the brake fluid for the following conditions, indicating brake fluid contamination:
    1. Fluid Separation, Indicating 2 Types Of Fluid Are Present:
      • Swirled Appearance - Oil-Based Substance
      • Layered Appearance - Silicone-Based Substance
    2. Fluid Discoloration:
      • Cloudy Appearance - Moisture
      • Dark Appearance/Suspended Particles In Fluid - Dirt, Rust, Corrosion, Brake Dust
      • Inspect The Master Cylinder Reservoir Cap Diaphragm And The Reservoir-To-Master Cylinder Grommets For Swelling, Indicating Fluid Contamination.
    Do any of the above conditions exist? If so, go to step  5 . If not, go to step  6 .
  4. Inspect the brake fluid for the following conditions, indicating brake fluid contamination:
    1. Fluid Separation, Indicating Two Types Of Fluid Are Present:
      • Swirled Appearance - Oil-Based Substance
      • Layered Appearance - Silicone-Based Substance
    2. Fluid Discoloration:
      • Cloudy Appearance - Moisture
      • Dark Appearance/Suspended Particles In Fluid - Dirt, Rust, Corrosion, Brake Dust Inspect The Master Cylinder Reservoir Cap Diaphragm And The Reservoir-To-Master Cylinder Grommets For Swelling, Indicating Fluid Contamination.
    Do any of the above conditions exist? If so, go to next step. If not, go to step  12 .
  5. Flush the hydraulic brake system. If the brake fluid WAS contaminated with an oil-based or a silicone-based fluid, indicated by fluid separation and/or a swollen master cylinder reservoir cap diaphragm and/or swollen reservoir-to-master cylinder grommets, perform the following steps:
    1. Remove ALL of the following components listed. Each component contains internal rubber seals/linings which have been contaminated.
    2. Clean out the hydraulic brake pipes using denatured alcohol, or equivalent.
    3. Dry the brake pipes using non-lubricated, filtered air.
    4. Repair or replace ALL of the following components listed. Each component contains internal rubber seals/linings which have been contaminated:
      • Master Cylinder Overhaul Or Master Cylinder Replacement
      • Brake Master Cylinder Reservoir: Clean The Brake Master Cylinder Reservoir Using Denatured Alcohol, Or Equivalent, Then Dry The Reservoir Using Non-Lubricated, Filtered Air, Or If Necessary, Replace The Brake Master Cylinder Reservoir
      • Replace The Brake Master Cylinder Reservoir Cap Diaphragm
      • Front Brake Hoses
      • Rear Brake Hoses
      • Front Brake Caliper Overhaul
      • Rear Brake Caliper Overhaul
      • Brake Pressure Modulator Valve (BPMV)
      See REMOVAL & INSTALLATION  or OVERHAUL  for appropriate procedures.
    If the brake fluid was not contaminated with an oil-based fluid, but was contaminated with water or dirt, rust, corrosion, and/or brake dust, replace the brake master cylinder reservoir cap diaphragm which may have allowed moisture or dirt to enter the system. Refill and bleed the hydraulic brake system. After necessary repairs are completed, go to step  9 .
  6. Inspect the following hydraulic brake system components for external fluid leaks. Repair or replace any of the components found to be leaking brake fluid:
    • Master Cylinder
    • Brake Master Cylinder Reservoir Cap Diaphragm
    • Brake Hose
    • Brake Pipe Replacement
    • Brake Caliper Overhaul
    • Pressure Modulator Valve (BPMV)
    See REMOVAL & INSTALLATION  or OVERHAUL  for appropriate procedures. If you repaired or replaced any of the brake system components listed, bleed the hydraulic brake system. While bleeding the hydraulic brake system, observe for the following conditions:
    • The presence of air in the system at a bleeder valve location other than at the repair location, except if the brake master cylinder was replaced.
    • An unrestricted and even flow of brake fluid per axle during the bleeding procedure.
    Did you find and correct a condition? If so, go to next step. If not, go to step  12 .
  7. Was there air in the system at a bleeder valve location other than at the repair location, except if the brake master cylinder was replaced? If so, go to step  19 . If not, go to next step.
  8. Was the flow of brake fluid unrestricted and even per axle during the bleeding procedure? If so, go to next step. If not, go to step  10 .
  9. Inspect the hydraulic function of the brake calipers for proper operation. Was the hydraulic function of the brake calipers operating properly? If so, go to step  21 . If not, go to step  14 .
  10. Was the flow of brake fluid restricted or uneven through front axle hydraulic components during the bleeding procedure? If so, go to step  13 . If not, go to next step.
  11. Was the flow of brake fluid restricted or uneven through rear axle hydraulic components during the bleeding procedure? If so, go to step  17 .
  12. Inspect the hydraulic function of the brake calipers for proper operation. Was the hydraulic function of the brake calipers operating properly? If so, go to step  15 . If not, go to next step.
  13. Determine if the brake caliper is restricting the flow of brake fluid and/or not operating properly:
    1. Raise and support the vehicle.
    2. Remove the tire and wheel assemblies.
    3. Open the suspected caliper bleeder valve.
    4. Using a large C-clamp, compress the caliper piston and observe for an unrestricted flow of brake fluid and for free movement of the caliper piston.
    5. Close the caliper bleeder valve.
    Was the flow of brake fluid unrestricted and did the caliper piston move freely? If so, go to step  17 . If not, go to next step.
  14. Repair or replace any brake caliper that was not operating properly. After repairs are complete, go to step  21 .
  15. Bleed the hydraulic brake system to observe for the presence of air in the system and to observe for an unrestricted and even flow of brake fluid per axle during the bleeding procedure. Was there air in the system? If so, go to step  19 . If not, go to next step.
  16. Was the flow of brake fluid unrestricted and even per axle during the bleeding procedure? If so, go to step  21 . If not, go to next step.
  17. Inspect the hydraulic brake pipes and flexible brake hoses for signs of a fluid restriction; such as being bent, kinked, pinched or damaged. Replace any of the hydraulic brake pipes and/or flexible brake hoses found to be bent, kinked, pinched or damaged:
    • Brake Hoses
    • Rear Brake Pipes
    See REMOVAL & INSTALLATION  for appropriate procedures. If none of the hydraulic brake pipes or flexible brake hoses were visibly bent, kinked, pinched or damaged, replace the hydraulic brake flex hose at the restricted location. Did you find and correct a condition? If so, go to step  21 . If not, go to next step.
  18. Replace the Brake Pressure Modulator Valve (BPMV), in order to correct the hydraulic brake dynamic rear proportioning mechanical operation. After repairs are complete, go to step  21 .
  19. Inspect the hydraulic brake system components for brake fluid seepage at a seal and/or fitting location, which may have drawn air into the system. Inspect the hydraulic brake system components for evidence of a recent repair, which may have introduced air into the system. Repair or replace any of the components found to be installed incorrectly or seeping brake fluid. Did you find and correct a condition? If so, go to step  21 . If not, go to next step.
  20. Inspect the brake master cylinder for internal fluid leaks. See BRAKE SYSTEM INTERNAL LEAK TEST  under SYSTEM TESTING. Repair or replace the brake master cylinder if it is found to be leaking brake fluid internally. Did you find and correct a condition? If so, go to next step. If not, go to SYMPTOMS (HYDRAULIC BRAKES)  under TROUBLE SHOOTING.
  21. Install or connect components that were removed or disconnected during diagnosis. Did you complete the operation? If so, system is okay. If not, go to step  2 .
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.