2005 Buick Century Brake Booster

You need to remove the Brake Master Cylinder from the vehicle, secure the mounting flange of the brake master cylinder in a bench vise so that the rear of the primary piston is accessible, 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, use a smooth, round-ended tool to 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, apply low pressure, non-lubricated, filtered air into the front outlet port, and the return spring, and then discard the primary piston assembly, the piston retainer, and the seals and seal retainer from the secondary piston.

You need to secure the mounting flange of the brake master cylinder in a bench vise so that the rear of the primary piston is accessible, remove the master cylinder reservoir cap and diaphragm, install suitable fittings to the master cylinder ports that match the type of flare seat required and also provide for hose attachment and transparent hoses to the fittings installed to the master cylinder ports, then route the hoses into the master cylinder reservoir, fill the master cylinder reservoir to at least the half-way point 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 ensure that the ends of the transparent hoses running into the master cylinder reservoir are fully submerged in the brake fluid. Then you can use a smooth, round-ended tool to depress and release the primary piston as far as it will travel, a depth of about 25 mm (1 in), several times, and observe the flow of fluid coming from the ports, continue to depress and release the primary piston until fluid flows freely from the ports with no evidence of air bubbles, remove the transparent hoses from the master cylinder reservoir, install the master cylinder reservoir cap and diaphragm, remove the fittings with the transparent hoses from the master cylinder ports, wrap the master cylinder with a clean shop cloth to prevent brake fluid spills and remove the master cylinder from the vise.

The recommended torque is 27 Nm (20 ft. lbs.).