Flushing Brake System

2004 Oldsmobile Bravada AWDSECTION Flushing Brake System
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. Inspect the brake fluid for the following conditions, indicating brake fluid contamination:
    1. Fluid separation, indicating two types of fluid are present; a substance other than the recommended brake fluid has been introduced into the brake hydraulic system.
      • Swirled appearance - oil-based substance.
      • Layered appearance - silicone-based substance.
    2. Fluid discoloration, indicating the presence of moisture or particles that have been introduced into the brake hydraulic system.
      • Cloudy appearance - moisture.
      • Dark appearance/suspended particles in fluid - dirt, rust, corrosion, brake dust.
  2. Inspect the master cylinder reservoir cap diaphragm and the reservoir-to-master cylinder grommets for swelling, indicating brake fluid contamination.
  3. If the brake fluid was contaminated with an oil-based or a silicone-based substance, indicated by fluid separation and/or a swollen master cylinder reservoir cap diaphragm and/or swollen reservoir-to-master cylinder grommets, perform the following:
    1. Remove all of the following components listed from the vehicle. Each component contains internal rubber seals/linings which have been contaminated by the contaminated brake fluid in the brake hydraulic system:
      • Master Cylinder
      • Brake Hoses
      • Brake Calipers
      • Brake Pressure Modulator Valve (BPMV)
      See REMOVAL & INSTALLATION  for proper procedures.
    2. Clean out all 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 and install them to the vehicle. Each component contains internal rubber seals/linings which have been contaminated by the contaminated brake fluid in the brake hydraulic system:
      • Master Cylinder Overhaul or Master Cylinder Replacement; also perform the following: Clean the brake master cylinder reservoir using denatured alcohol, or equivalent, then dry the reservoir using non-lubricated, filtered air. Inspect the reservoir for cracks and/or damage and replace if necessary.
      • Replace the brake master cylinder reservoir cap diaphragm.
      • Brake Hoses
      • Brake Calipers
      • Brake Pressure Modulator Valve (BPMV)
      See REMOVAL & INSTALLATION  and OVERHAUL  for proper procedures.
  4. If the brake fluid was not contaminated with an oil-based or a silicone-based substance, but was contaminated with water or dirt, rust, corrosion, and/or brake dust, replace the brake master cylinder reservoir cap diaphragm. The diaphragm may have allowed the moisture or particles to enter the hydraulic system.
  5. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11(R), GM U.S. P/N 12377967, or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
  6. Pressure bleed the hydraulic brake system. Begin the procedure with the pressure bleeder reservoir filled to the maximum-fill level with the correct brake fluid as indicated.
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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.