GM 18060787
Master Cylinder

Place the Brake Master Cylinder mounting flange into a bench vise while providing access to the rear side of the primary Piston for bench bleeding purposes. Put each end of suitable fittings onto the master cylinder ports to match brake system requirements then connect hoses made for these ports. Lead the transparent hoses from these fittings into the main cylinder reservoir. Put delco supreme 11 brake fluid or an equivalent dot-3 brake fluid from a sealed container into the reservoir up to the halfway mark while keeping the hose ends in the fluid. Push and release the smooth tool into the primary Piston unit about a quarter inch several times then check for fluid output from the ports. Depressing the primary Piston needs more force because air is leaving both pistons which shortens its travel. Keep going with this technique until the ports release fluid without air trapped inside. When done bleed the fluid system through all transparent ports then apply the reservoir cap and diaphragm before disconnecting fittings with the hoses. Protect the master cylinder from brake fluid leaks by wrapping it with a soft cloth before removing from the vise.

Wrap the master cylinder with a clean shop cloth to prevent brake fluid spills.

Remove the master cylinder mounting nuts and take the master cylinder out of the vehicle.

Remove it from the vehicle and secure the mounting flange in a bench vise, ensuring the rear of the primary piston is accessible.

Reconnect the electrical connector to the brake fluid level sensor and finally bleed the brake system.

Bench bleed the master cylinder.

Reconnect the electrical connector to the fluid level switch.