GM 19209239
Master Cylinder

Put the park brake on and block the wheels before working on the Brake Master Cylinder (Hydraulic Boost). Put a plug over brake pipe ends to block brake fluid from escaping when you detach the hose connection to the Brake Fluid Level Sensor. You should unhook the brake lines from the master cylinder then seal the open brake pipe ends. Take the master cylinder out of the car by removing its mounting nuts first and then taking out the master cylinder reservoir. To begin installation you need to put the master cylinder reservoir in place first. Before putting the master cylinder back into the vehicle perform a fluid drainage operation called bench bleed. Secure the master cylinder mounting bolts by tightening them to 36 n.m (27 ft lb). Put together the connected brake pipes by adding the rubber caps back at the exposed ends then tightening the fittings to 25 n.m (18 lb ft). Join the brake fluid sensor electrical connector as you run hydraulic brake system bleeding. Complete the job by releasing the parking break and moving the wheels once free.

Lock the parking brake and use wheel blocks to start replacing the Brake Master Cylinder (Hydraulic Boost). You need to first disconnect the electrical sensor of the brake fluid level. Put a rubber seal or plug over the open brake tube ports to keep out dirt and fluid loss before taking the brake lines apart from the master cylinder. Remove the master cylinder from the vehicle by unplugging its open brake pipes and removing the mounting nuts. After installing the master cylinder reservoir you need to bench bleed the master cylinder prior to reinstallation in the car. Secure the master cylinder mounting nuts by tightening them to 33 nm (24 ft. Lbs.). Attach the brake pipes to their ends with exposed rubber caps or plugs. Tighten the pipe fittings also to 25 nm (18 ft. Lbs.). Connect the brake fluid sensor electrical connection and then perform hydraulic brake system bleeding followed by unlocking the parking brake and removing wheel obstructions.

First apply the parking brake and disable the wheels before working on the hydraulic boost master cylinder. To prevent brake fluid loss seal the exposed brake pipe openings with a rubber cap before detaching the Brake Fluid Level Sensor connector. Seal the brake pipe openings at both ends by plugging them after you disconnect the brake pipes from their connection with the master cylinder. Pull out the master cylinder by removing its mounting nuts before you take it from the vehicle and separate the master cylinder reservoir. Begin the installation process by adding the master cylinder reservoir first and then bench bleed the master cylinder. Reinstall the master cylinder into its vehicle position and fasten it firmly with mounting nuts at 33 nm (24 ft. Lbs). Connect the brake pipes by putting their open ends together and tighten the pipe fittings to 25 nm (18 ft. Lbs.). Connect the Brake Fluid Level Sensor electrical connector and drain the brake hydraulic system. To end the process release the parking brake and take away wheel obstructions.

To remove the Brake Master Cylinder (Vacuum Boost), you need to first apply the park brake and block the wheels. Remove the electrical connector of the Brake Fluid Level Sensor and braking pipes from the master cylinder. Screw a rubber cap or plug to the brake pipe fitting ends where they are exposed so that brake fluid does not leak out and so that the brake pipe is sealed. Dispose of the master cylinder nuts and remove it away from the vehicle along with the master cylinder reservoir being removed. For installation, begin by wrapping the master cylinders reservoir before bench bleeding the master cylinder and reinstall it back in the vehicle. Mount the arms on the master cylinder, and tighten the master cylinder mounting nuts to 33 nm (24 ft. Lbs.). Pry or pull the rubber cap or plug off the exposed brake pipe fitting ends, hook up the brake pipes on the respective units, and tighten the brake fittings to 25 nm (18 ft. Lbs.). Return the electrical connector back to the Brake Fluid Level Sensor, bleed hydraulic brake system, lastly releasing the park brake and unblocking the wheels.

You can work on the Brake Master Cylinder's primary Piston by fixing the mounting flange in a bench vise to expose its backside. Put on suitable brake fittings that fit into the master cylinder ports. These fittings should match the necessary flare seat to hold tubing securely. Connect transparent hoses to the fittings of the Brake Master Cylinder and feed them toward the reservoir. Pour delco supreme ii® (GM P/N 12377967) or dot-3 brake fluid from a pure source up to the halfway point of the reservoir while submerging both ends of the hoses inside. Push and release the smooth primary Piston tool several times to a depth of 25 mm using a raw round tip as fluid exits the ports during bleeding. Air removal causes Piston travel to decrease and actions to push forward to increase. Take successive action with the tool until brake fluid emerges without aeration from the port outlets. Reinstall the master cylinder reservoir parts and disconnect the hose fittings from their ports. Then wrap the master cylinder with a clean cloth to prevent spills while taking it out from the vise.

When fixing the Brake Master Cylinder you should place its mounting flange into a workbench vise for stability while making sure to reach the primary Piston's back side. Set up the required fittings that match the master cylinder flare-seat and let you connect brake hoses to each port. Set transparent hoses to these fittings then guide them into the reservoir space. Pump delco supreme 11 brake fluid or equivalent dot-3 fluid up to the halfway point of the reservoir from clean labeled containers. Make sure the fluid end points dip completely under fluid. Depress and release the primary Piston with a smooth round tool up to 25 mm in Piston travel as fluid flows from the ports to complete this procedure. Decreased movement of the primary Piston needs more force while the bleeding process clears trapped air. Repeat this step until fluid appears without air pockets in the openings. Reinstall all parts back into the reservoir space after taking the hoses and master cylinder reservoir cap out. Lastly pull the fittings off their ports with the hoses and put a clean cloth over the master cylinder while dismounting it from the vise.

You should first use the park brake and block the wheels when changing the Brake Master Cylinder (Vacuum Boost). Take off the plug from the Brake Fluid Level Sensor and remove the brake pipes attached to the master cylinder. Put a rubber cap or plug on the brake pipe fittings that are now open to keep brake fluid from leaking and contaminants out. Remove the nuts that hold the master cylinder in place and then lift out the master cylinder from the vehicle along with its reservoir. Put the master cylinder reservoir back in its place, and then perform a bench bleed on the master cylinder. Put the master cylinder into the vehicle and fasten it in place with the mounting nuts, turning them to 33 nm or 24 ft. Lbs. Take off the rubber cap or plug from the uncovered brake pipe openings, and then attach the brake pipes, tightening each fitting to 25 nm (18 ft. Lbs.). Carefully reconnect the electrical connector to the Brake Fluid Level Sensor, proceed to bleed the hydraulic brake system, and at last, release the park brake and take off any wheel blocks.

Attach transparent hoses to the fittings and route them into the reservoir.

Inspect both the diaphragm and reservoir cap for cuts, cracks, nicks, or deformation, and replace any affected components.

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.

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

Bench bleed the master cylinder.

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.

The effort to depress the primary piston will increase and its travel will decrease.

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

Discard the primary piston assembly, piston retainer, and seals.

Reconnect the electrical connector to the brake fluid level sensor.

Bench bleed the master cylinder.