2006 GMC Yukon Brake Master Cylinder

You need 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 to the fittings installed to the master cylinder ports, route the hoses into the master cylinder reservoir, fill the master cylinder reservoir to at least the half-way point, 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 until fluid flows freely from the ports with no evidence of air bubbles, remove the transparent hoses, install the master cylinder reservoir cap and diaphragm, remove the fittings with the transparent hoses and the master cylinder from the vise.

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.

You should 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.

You need to install the fluid level sensor until the locking tabs snap into place, and connect the electrical connector to the fluid level sensor.

You need to 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, remove the reservoir cap and diaphragm, inspect the reservoir cap and diaphragm, remove the master cylinder reservoir from, depress the primary piston and remove the piston retainer, remove the primary piston assembly, 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.