2005 Buick Rainier Brake Master Cylinder

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, fill the master cylinder reservoir to at least the halfway point 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, 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, remove the transparent hoses from the master cylinder reservoir, install the master cylinder reservoir cap and diaphragm and remove the fittings with the transparent hoses from the master cylinder ports and the master cylinder from the vise.

The recommended torque is 36 Nm (27 ft-lbs).

You should ensure that the fluid sensor is fully seated before releasing the snap ring and install the fluid level sensor and the electrical connector to the fluid level sensor.

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 visually 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, 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.