Hydraulic System Flushing
WARNING: This page is about a different car, the 2002 GMC Safari and 2002 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
- Inspect brake fluid for the following conditions, indicating brake fluid contamination:
- 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):
- 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 or brake dust).
- 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):
- Inspect master cylinder reservoir cap diaphragm and the reservoir-to-master cylinder grommets for swelling, indicating brake fluid contamination.
- If 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:
- 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. See MASTER CYLINDER under REMOVAL & INSTALLATION.
- Front brake hose.
- Rear brake hose.
- Front brake caliper. See FRONT BRAKE CALIPER under REMOVAL & INSTALLATION.
- Wheel cylinder. See WHEEL CYLINDER under REMOVAL & INSTALLATION.
- Combination valve. See COMBINATION VALVE under REMOVAL & INSTALLATION.
- Brake Pressure Modulator Valve (BPMV). See appropriate ANTI-LOCK article.
- Clean out all the hydraulic brake pipes using denatured alcohol (or equivalent).
- Dry brake pipes using non-lubricated, filtered air.
- 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. See MASTER CYLINDER under OVERHAUL. Also clean brake master cylinder reservoir using denatured alcohol, then dry reservoir using non-lubricated, filtered air. Inspect reservoir for cracks and/or damage and replace, if necessary. See MASTER CYLINDER under REMOVAL & INSTALLATION. Replace brake master cylinder reservoir cap diaphragm.
- Replace front brake hose.
- Replace rear brake hose.
- Overhaul or replace front brake caliper. See BRAKE CALIPER under OVERHAUL or FRONT BRAKE CALIPER under REMOVAL & INSTALLATION.
- Replace wheel cylinder. See WHEEL CYLINDER under REMOVAL & INSTALLATION.
- Replace combination valve. See COMBINATION VALVE under REMOVAL & INSTALLATION.
- Replace Brake Pressure Modulator Valve (BPMV). See appropriate ANTI-LOCK article.
- 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:
- If 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 brake master cylinder reservoir to the maximum fill level with 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 DOT-3 brake fluid. See BLEEDING BRAKE SYSTEM .