GM 19209230
Master Cylinder

Place the Brake Master Cylinder's mounting flange into the vise with care to work on its backside and the primary Piston. Connect suitable fittings to the master cylinder ports using the right seat connections to allow hose attachment. Then remove the cap and diaphragm from the reservoir. Connect transparent hoses to the required fittings on the master cylinder then direct them into the reservoir for a service repair. Insert both brake fluid hoses into clean delco supreme 11(R) brake fluid (GM P/N 12377967) until they reach halfway into the reservoir and submerge their ends fully. With a smooth round-ended tool, press and release the primary Piston multiple times while monitoring fluid output from the ports. The force needed to push the Piston will build up while its movement becomes limited as air comes out of the primary and secondary Piston chambers. Perform this action until the ports show continuous flow of fluid without bubbles. Return the master cylinder reservoir cap and diaphragm before detaching the fittings and hoses from their ports. For cleanup, cover the master cylinder with a shop cloth and take it off the vise.

First disconnect electrical power from the brake fluid sensor while taking off the brake pipes from the master cylinder. Seal exposed pipe ends with rubber caps or plugs to stop fluid loss and contamination. Insert plugs in all brake pipe fittings before you remove the 2 mounting nuts holding the master cylinder and take it out. Take the reservoir away if it will serve the same purpose later. Install the Brake Master Cylinder reservoir to the master cylinder if it was detached then perform bench bleed operations before attaching it to the vacuum Brake Booster according to fastener notice guidelines in service precautions. Secure the master cylinder with 2 nuts by turning them to 25 nm (18 ft. Lbs.). Then join the brake pipes to the master cylinder using their fittings and tighten them to 33 nm (24 ft. Lbs.). Reconnect the electrical connector to the level sensor and use the correct process to push out air from the braking system.

Disconnect the electrical connector from the brake fluid level sensor and the brake pipes from the master cylinder, ensuring to install a rubber cap or plug on the exposed brake pipe fitting ends to prevent fluid loss and contamination.

A smooth, round-ended tool is used to depress and release the primary piston several times.

A smooth, round-ended tool.

Attach the brake master cylinder reservoir to the master cylinder if it was removed, then bench bleed the master cylinder.

Use a smooth, round-ended tool to depress the primary piston and remove the piston retainer, followed by the primary piston assembly from the cylinder bore.

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

Remove the reservoir from the master cylinder.

Depress the primary piston to a depth of about 25 mm (1 inch) several times.

A smooth, round-ended tool.

Plug the open brake pipe fitting ends, remove the 2 master cylinder mounting nuts, and take out the master cylinder.