2005 Buick LeSabre Brake Master Cylinder

You should 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 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container, assemble the lubricated, new primary seal and retainer, and new secondary seal onto the secondary piston, install the lubricated return spring and secondary piston assembly into the cylinder bore, install the lubricated, new primary piston assembly into the cylinder bore, depress the primary piston and install the new piston retainer and install the master cylinder to the vehicle.

You should disconnect the electrical connector from the brake fluid level sensor, depress the retaining tabs on the end of the brake fluid level sensor, and press the sensor through the reservoir to remove it.

You should inspect the brake fluid level through the brake master cylinder reservoir. If the brake fluid level is at or below the half-full point during routine fluid checks, the brake system should be inspected for wear and possible brake fluid leaks. If the brake fluid level is at or below the half-full point during routine fluid checks, and an inspection of the brake system did not reveal wear or brake fluid leaks, the brake fluid may be topped off up to the maximum-fill level. If brake system service was just completed, the brake fluid may be topped off up to the maximum-fill level. If the brake fluid level is above the half-full point, adding brake fluid is not recommended under normal conditions. If the brake fluid is to be added to the master cylinder reservoir, You should clean the outside of the reservoir on and around the reservoir cap before removing the cap and diaphragm. You should use only Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.

You should remove the brake master cylinder from the vehicle, secure the mounting flange of the brake master cylinder in a bench vise, clean the outside of the master cylinder reservoir on and around the reservoir cap before removing the cap and diaphragm, remove the reservoir cap and diaphragm from the reservoir, inspect the reservoir cap and diaphragm for the following conditions, remove the master cylinder reservoir from the master cylinder, depress the primary piston and remove the piston retainer, remove the primary piston assembly from the cylinder bore, plug the cylinder inlet ports and the rear outlet port and discard the primary piston assembly, the piston retainer, and the seals and seal retainer from the secondary piston.

You should remove the master cylinder from the vehicle, remove the fluid level sensor, drain the brake fluid from the master cylinder reservoir, carefully tap out the reservoir retaining pins until clear of the reservoir, remove the reservoir from the master cylinder and remove the seals from the master cylinder reservoir.