OEM 2003 GMC Envoy Brake Master Cylinder

2003 GMC Envoy Brake Master Cylinder Parts Questions & Experts Answers

• Q: How to overhaul the brake master cylinder on 2003 GMC Envoy?

  A: Before working on a Brake Master Cylinder you must remove it from the vehicle and get the mounting flange into a bench vise where you need access to the rear part of the primary Piston. Prior to removing the cap and diaphragm from the master cylinder reservoir's outside you should clean it thoroughly to check for cuts or cracks or nicks or deformities and replace damaged parts as needed. Start by disconnecting the master cylinder reservoir before using a smooth tool with round ends to push down the primary Piston and then remove the Piston retainer followed by the primary Piston assembly from the cylinder bore. Use low pressure filtered air to blow through the front outlet port while plugging all cylinder inlet ports and the rear outlet port in order to remove the secondary Piston along with its primary Piston and secondary seals and return spring. Keep the primary Piston components for discard. Denoaturred alcohol cleans and inspects the master cylider and secondary Piston and return spring for cracks pitting scoring or corrosion before master cylinder replacement. The bore as well as the secondary Piston and return spring and all overhaul parts require application of delco supreme 11, gm U.S. P/N 12377967, gm canada P/N 992667, or equivalent dot-3 brake fluid from a clean, sealed container after drying the components with non-lubricated, filtered air. Position the new primary seal with the retainer component to the secondary Piston before you install the lubricated return spring and secondary Piston assembly into the cylinder bore then add the lubricated new primary Piston assembly . Use a round-ended tool to depress the primary Piston which installs the new Piston retainer before you reconnect the master cylinder reservoir and its cap and diaphragm. The completion of the installation process involves putting the master cylinder into its original position on the vehicle.