Hydraulic Brake System Flushing

WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, and 2003 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Prior to performing any work, review warnings, cautions and notes. See BRAKE BLEEDING WARNINGS, CAUTIONS & NOTES under SERVICE PRECAUTIONS.

Inspect the brake fluid for the following conditions, indicating brake fluid contamination:
1. Fluid separation indicating 2 types of fluid are present; a substance other than the recommended brake fluid has been introduced into the brake hydraulic system:
  - If its a swirled appearance, then it is an oil-based substance.
  - If its a layered appearance, then it is a silicone-based substance.
2. Fluid discoloration, indicating the presence of moisture or particles that have been introduced into the brake hydraulic system:
  - If its a cloudy appearance, then its due to moisture.
  - If its a dark appearance/suspended particles in fluid, then its due to 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:
  - See MASTER CYLINDER under REMOVAL & INSTALLATION.
  - See BRAKE HOSE under REMOVAL & INSTALLATION.
  - See BRAKE CALIPER under REMOVAL & INSTALLATION.
  - See BRAKE PRESSURE MODULATOR VALVE under REMOVAL & INSTALLATION in appropriate ANTI-LOCK article.
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:
  - See MASTER CYLINDER under OVERHAUL or MASTER CYLINDER under REMOVAL & INSTALLATION. 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. See MASTER CYLINDER RESERVOIR under REMOVAL & INSTALLATION. Replace the brake master cylinder reservoir cap diaphragm.
  - See BRAKE HOSE under REMOVAL & INSTALLATION.
  - See BRAKE CALIPER under OVERHAUL; or BRAKE CALIPER under REMOVAL & INSTALLATION.
  - See BRAKE PRESSURE MODULATOR VALVE under REMOVAL & INSTALLATION in appropriate ANTI-LOCK article.
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®, 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. See MANUAL BLEEDING or PRESSURE BLEEDING .