GM 18029859
Overhaul Kit

Before fixing the Brake Master Cylinder take it off from the auto and position the mounting flange in a workbench vise with access to the back of the primary Piston. Check the outside area near the master cylinder reservoir cap before unscrewing it to look for damage on both the cap and diaphragm. Replace any damaged components in this process. Use a suitable tool to work a smooth round tip towards the primary Piston which permits the removal of the Piston retainer and primary Piston assembly. Place plugging devices on all cylinder ports while using low pressure filtered air to blow out the secondary Piston and its packing rings plus spring and Piston primary . Remove the primary Piston device plus its retainer and seals from the secondary Piston. Use denatured alcohol to clean master cylinder inside and out as well as secondary Piston and return spring. Check for cracks, damage, and corrosion before replacing the master cylinder when problems are detected during inspection. After cleaning with filtered air, apply brake fluid delco supreme 118 equivalent dot-3 (Part 12377967) to the master cylinder bore and its components including the secondary Piston , return spring, and all parts. Position the lubricated new primary seal with retainer on top of the secondary Piston then place the secondary seal underneath while adding the lubricated return spring and secondary Piston unit in the cylinder bore until you can insert the lubricated new primary Piston assembly. Thread the primary Piston assembly through the master cylinder opening while pressing it down gently using a smooth tool before installing the new Piston retainer. Replace the reservoir parts then put the master cylinder back.

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

Bench bleed the master cylinder.

Install suitable fittings to the master cylinder ports that match the required flare seat and allow for hose attachment.

Drain all brake fluid from the master cylinder reservoir.

Replace the master cylinder if any issues are found.

Tighten the brake pipe fittings to 32 Nm (24 ft. lbs.).

Tighten the plugs before allowing the piston to return.

Clean the interior and exterior of the master cylinder, secondary piston, and return spring in denatured alcohol, inspecting for cracks, scoring, pitting, or corrosion.

Replace the master cylinder if any issues are found.

Install the master cylinder to the brake booster, then install the mounting nuts and tighten them to 29 N.m (21 lb ft).

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

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