2007 GMC Sierra 3500 HD Brake Master Cylinder

When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11(R), General Motors (GM) P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.

The procedure is to 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, install transparent hoses, fill the master cylinder reservoir, ensure that the ends of the transparent hoses, depress and release the primary piston, depress and release the primary piston, remove the transparent hoses, install the master cylinder reservoir cap and diaphragm, remove the fittings with the transparent hoses and then remove the master cylinder from the vise.

The procedure is to visually inspect the brake fluid level through the brake master cylinder reservoir and then clean the outside of the reservoir on and around the reservoir cap before removing the cap and diaphragm.

You should clean the reservoir with denatured alcohol, dry the reservoir with non-lubricated, lubricate the new seals and the outer surface area of the reservoir-to-housing barrels, install the lubricated seals, install the reservoir, install the reservoir retaining pins to secure the reservoir, install the master cylinder and then bleed the hydraulic brake system.

You should apply the brake pedal several times, remove the brake fluid from the brake master cylinder reservoir and then discard the brake fluid into an approved container.