2005 Buick Rainier Brake Booster

You should remove the Brake Master Cylinder, 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, remove the master cylinder reservoir from the master cylinder, depress the primary piston, remove the piston retainer and the primary piston assembly, plug the cylinder inlet ports and the rear outlet port, remove the secondary piston with the primary and secondary seals, and the return spring and discard the primary piston assembly, the piston retainer, and the seals and seal retainer from the secondary piston.

You should secure the mounting flange of the brake master cylinder in a bench vise, remove the master cylinder reservoir cap and diaphragm, install suitable fittings to the master cylinder ports and the transparent hoses to the fittings, fill the master cylinder reservoir to at least the half-way point with Delco supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid, ensure that the ends of the transparent hoses running into the master cylinder reservoir are fully submerged in the brake fluid, depress and release the primary piston as far as it will travel, a depth of about 25 mm (1 inch), several times, depress and release the primary piston, remove the transparent hoses, install the master cylinder reservoir cap and diaphragm and remove the fittings with the transparent hoses and the master cylinder.