GM 19209264
Master Cylinder

Secure the Brake Master Cylinder mounting flange to a bench vise with the Piston rear accessible for Brake Master Cylinder overhauls. Before you uninstall the master cylinder cap and diaphragm clean the reservoir's exterior to inspect their condition. Check for any cuts, cracks, nicks or damage and replace items that need replacement. Start by taking out the master cylinder reservoir. Then, push the primary Piston gently with a smooth cylindrical tool and remove its holder and assembly. Insert air plugs into several ports while connecting filtered low-pressure air to the front port to blow out the secondary Piston plus its primary and secondary seals and return spring for disposal along with the primary Piston assembly and Piston retainer. Wipe the master cylinder inside and out with denatured alcohol then inspect the secondary Piston and return spring for damage while replacing the master cylinder if issues exist. Dry all parts with filtered non-lubricated air followed by delco supreme 11(R) fluid (GM P/N 12377967) to lubricate the master cylinder chamber, secondary Piston, return spring, and all components. Install the new primary seal and retainer with secondary seal onto the secondary Piston before inserting the lubricated return spring and secondary Piston assembly into the bore. Keep these parts moist with new primary Piston assembly and complete the assembly process. Press down the primary Piston using a smooth tool. Insert the new Piston retainer and reinstall both the reservoir and its parts and finally put back your master cylinder.

Reattach the master cylinder reservoir and its cap and diaphragm before reinstalling the master cylinder to the vehicle.

Drain all brake fluid from the master cylinder reservoir and remove the reservoir.

Drain all brake fluid from the master cylinder reservoir and remove the reservoir.

Fill the master cylinder reservoir with brake fluid and bleed the brake system.

Remove the transparent hoses from the reservoir, reinstall the master cylinder reservoir cap and diaphragm, and detach the fittings with the hoses from the ports.

First, disconnect the brake pipes from the master cylinder and the fluid level sensor electrical connector.