You need to clean the interior and exterior of the master cylinder, the secondary piston, and the return spring in denatured alcohol, or equivalent, inspect the master cylinder bore, inlet and outlet ports, the secondary piston, and the return spring for cracks, scoring, pitting, and/or corrosion, replace the master cylinder if any of these conditions exist, dry the master cylinder and the individual components with non-lubricated, filtered air, lubricate the master cylinder bore, the secondary piston, the return spring, and all of the individual overhaul components with Delco Supreme II, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container and assemble the lubricated, new primary seal and retainer, and new secondary seal onto the secondary piston. Then you can install the lubricated return spring and secondary piston assembly into the cylinder bore and the lubricated, new primary piston assembly into the cylinder bore, use a smooth, round-ended tool to depress the primary piston and install the new piston retainer, and then install the master cylinder reservoir to the master cylinder, the reservoir cap and diaphragm to the reservoir and the master cylinder to the vehicle.
By BobGM Specialist
01/11/2022