GM 25952633
Master Cylinder

Replace the Brake Master Cylinder of 2.4l non hybrid and 3.6l engines by first removing and setting aside the radiator surge tank while keeping the cooling system intact. Dissipate vacuum from the Brake Booster by taking out the vacuum check valve that fits into the booster grommet. You should disconnect the master cylinder electrical connector plus remove the secondary brake pipe cap and the master cylinder outlet port plug to secure the brake fluid during replacement work. Follow this process to disconnect the primary brake pipe fitting at the master cylinder. Take out all nuts from the master cylinder then pull it off. Check the master cylinder seal around the vacuum booster for wear then replace if found faulty. Put the Brake Master Cylinder reservoir onto its designated position on the master cylinder unit. Put the master cylinder in the vacuum Brake Booster and check if the master cylinder to barrel contact sits correctly before installing it permanently. Install the master hydraulic cylinder nuts before tightening them to 25 nm (18 lb ft). Then connect and secure the primary brake line attaching fitting to 32 nm (24 lb ft) while doing the same for the secondary brake line. Connect the vacuum check valve to the Brake Booster grommet after lubricating it with a little denatured alcohol when needed. Put in the radiator surge tank and let air out of the hydraulic brake system.

The Brake Master Cylinder replacement starts with depleting vacuum from the booster by removing its vacuum check valve. Disconnect the electrical connector from the brake fluid level indicator switch plus the master cylinder secondary brake pipe fitting. Seal the fitting with caps and close the outlet port to preserve the brake fluid. Apply this process to the connection of the main brake tube. Pull the master cylinder from its position when you unscrew all its mounting nuts first. Check for damage on the cylinder seal that connects the master cylinder to the vacuum Brake Booster. Replace if necessary. Take out the master cylinder reservoir when necessary. Place the Brake Master Cylinder reservoir onto the master cylinder if it was removed and carry out the bench bleeding process on the master cylinder. Place the master cylinder barrel seal correctly on the vacuum Brake Booster before attaching it. Secure the master cylinder nuts tightly to 25 n.m (18 lb ft). Fit the primary brake pipe connection first then the secondary one and fasten it using 20 n.m (15 lb ft) torque. Use denatured alcohol as a lubricant to place the vacuum check valve onto the grommet but stay away from using soap. Connect the brake fluid level indicator switch and let hydraulic brake fluid flow through the system.