GM 18047787
Master Cylinder

To replace Brake Master Cylinder; disconnect the electrical connector of Brake Fluid Level Sensor and the brake pipes from master cylinder in line, make sure to cap the exposed brake pipe fitting ends using a rubber cap or plug to avoid losing fluids vales due to spillage. Next, insert the open brake pipe fitting ends, remove 2 master cylinder mounting nuts, and remove the master cylinder. When the reservoir is to be used again, take it out of the master cylinder. For installation, connect the Brake Master Cylinder reservoir to the vacuum Brake Booster if was detached, bench bleed the master cylinder, then connect it to the vacuum Brake Booster and refer to the fastener notice in service precautions. Mount the master cylinder with the 2 mounting nuts with 25 nm (18 ft. Lbs) of torque, then drain the plugs from the brake pipes and attach them to the master cylinder and tighten the fittings to 33 nm (24 ft. Lbs.). Finally, reconnect the Brake Fluid Level Sensor electric connector and bleed the hydraulic brake system.

Insert safe fittings over all the ports first and ensure they will not harm the seal valleys. Securely support the master cylinder at its mounting points to prevent warping while using the hoses to insert new fluid into its reservoir. Use delco supreme ii brake fluid gm p/n 12377967 or dot 3 equivalent parts to avoid damage to rubber components in the hydraulic system since water reduces boiling point and petroleum-based fluids swell them. Place a new supply of delco supreme ii brake fluid gm p/n 12377967 into the reservoir and push the cylinders down to their bottom positions with a smooth rod to prevent damage to internal parts. Depress then release the pistons repeatedly until the port lets fluid flow freely without air bubbles through it.

Use Delco Supreme 11 (R) (GM P/N 12377967) or equivalent DOT-3 brake fluid from a clean, sealed container.

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.

Install the master cylinder onto the power booster, ensuring to follow the fastener notice for proper torque.

Install suitable fittings for hose attachment.

Remove the reservoir from the master cylinder.

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

Tighten them to 30 Nm (22 ft. lbs.).

A smooth, round-ended tool.