Hydraulic Brake System Flushing

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, 2004 Chevrolet Cab & Chassis Silverado, and 2003 GMC Sierra. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Refer to Brake Fluid Irritant Caution in Cautions and Notices.

NOTE: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

Inspect the brake fluid for the following conditions, indicating brake fluid contamination:
- 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
- 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
Inspect the master cylinder reservoir cap diaphragm and the reservoir-to-master cylinder grommets for swelling, indicating brake fluid contamination.
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.
  Refer to the procedures indicated.
  - Master Cylinder Replacement (Vacuum Boost) or Master Cylinder Replacement (Hydraulic Boost)
  - Brake Hose Replacement - Front
  - Brake Hose Replacement - Rear (Caliper) or Brake Hose Replacement - Rear (Jounce)
  - Brake Caliper Replacement - Front in Disc Brakes
  - Brake Caliper Replacement - Rear (1500 Series) or Brake Caliper Replacement - Rear (2500/3500 Series) in Disc Brakes
  - Brake Pressure Modulator Valve (BPMV) Replacement in Antilock Brake System
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.
  Refer to the procedures indicated.
  - Master Cylinder Overhaul , Master Cylinder Replacement (Vacuum Boost) or Master Cylinder Replacement (Hydraulic Boost) ; 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. Refer to Master Cylinder Reservoir Replacement .
    
    Replace the brake master cylinder reservoir cap diaphragm.
  - Brake Hose Replacement - Front
  - Brake Hose Replacement - Rear (Caliper) or Brake Hose Replacement - Rear (Jounce)
  - Brake Caliper Overhaul - Front or Brake Caliper Replacement - Front in Disc Brakes
  - Brake Caliper Overhaul - Rear (15 Series) , Brake Caliper Overhaul - Rear (25/35 Series) , Brake Caliper Replacement - Rear (1500 Series) or Brake Caliper Replacement - Rear (2500/3500 Series) in Disc Brakes
  - Brake Pressure Modulator Valve (BPMV) Replacement in Antilock Brake System
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 which may have allowed the moisture or particles to enter the hydraulic system.
Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11® (GM P/N 12377967) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
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. Refer to Hydraulic Brake System Bleeding (Manual) or Hydraulic Brake System Bleeding (Pressure) .