GM 19209252
Overhaul Kit

Before replacing the Brake Master Cylinder (Vacuum Boost), ensure the parking brake is on and the electrical wire at the Brake Fluid Level Sensor is disconnected. After this, disconnect the brake hoses and put caps on them to make sure there is no brake fluid leak or contamination. Unscrew the master cylinder mounting nuts, take out the master cylinder, and afterwards the master cylinder reservoir. First, put the master cylinder reservoir in place, and then bench bleed the master cylinder. Set the master cylinder in place, use the fastener notice as a reference to install the nuts, and tighten them to 36 n.m (27 lb ft). Remove the caps from the pipes, put the brake lines in place, and tighten them to 25 n.m (18 lb ft). Install the electrical connection on the Brake Fluid Level Sensor, bleed the brakes, and afterwards set the parking brake.

Fixing the top-end of the Brake Master Cylinder starts with locking the mounting flange in a workbench vise to reveal its back section. Install suitable fittings on the master cylinder ports to connect hoses by first removing the reservoir components. Set up transparent hoses to connect the fittings which enter the master cylinder reservoir. Pour clean delco supreme 110 (GM P/N 12377967) brake fluid or dot-3 equivalent from a sealed container until it reaches the half mark inside the reservoir while keeping brake hose ends completely dipped in the fluid. With a rounded tool press down and let go the primary Piston a few times while noting fluid exit from supply ports. Pressing the primary Piston becomes more challenging and its range shifts downward when you release air from both pistons. Push the primary Piston several times until bleeding fluid shows no air bubbles through the ports. Reinsert the master cylinder cover before placing each fitting back on the hose ports. Then remove the reservoir assemblies and bind all leakage areas with clean cloth before taking off the vise.

Reconnect the electrical connector to the brake fluid level sensor, bleed the hydraulic brake system, and finally, release the park brake and unblock the wheels.

Remove the master cylinder mounting nuts and take the master cylinder out of the vehicle, followed by the removal of the master cylinder reservoir.

Apply the parking brake and disconnect the electrical connection at the brake fluid level sensor.

Bench bleed the master cylinder.

Inspect these components for cuts, cracks, nicks, or deformation, replacing any affected parts.

Install the master cylinder, ensuring to follow the fastener notice in service precautions, and tighten the mounting nuts to 36 N.m (27 lb ft).

Remove the seals and the spring retainer along with the spring from the master cylinder body.

Assemble the lubricated new primary seal and retainer along with the new secondary seal onto the secondary piston.

Reconnect the electrical connection at the brake fluid level sensor, bleed the brakes, and release the parking brake.