How to Replace a Brake Master Cylinder in a Chevrolet S10

The master cylinder is the main storage unit of brake fluid for your Chevrolet S-10 truck. Any damage to the cylinder will result in a great loss of brake fluid and major problems with the brakes. You need to change the cylinder and its reservoir whenever this occurs. Because you are opening the brake system to air while doing this, you need to bleed the system of air afterward.

Instructions

1

Place rags on the floor underneath the cylinder to catch any fluid.

2

Loosen the tube nuts connecting the brake lines to the master cylinder using a flare nut wrench. Pull the lines away and either plug their open ends with rubber or wrap plastic bags around them to prevent contamination.

3

Remove the rear wheel anti-lock (RWAL) module if the truck has this type of brake system. The module is located near the cylinder; release its clip with a thin pointed tool and remove it from its mounting bracket. You don't need to remove its electrical connectors; just lay it somewhere safe.

4

Remove the two mounting nuts for the master cylinder, then set aside the isolation/dump valve and the bracket for the RWAL module. Make sure you don't bend or kink the hydraulic lines as you disconnect these and remove the module. Remove the reservoir cover and diaphragm from the cylinder and properly dispose of any fluid remaining in the module.

5

Fill the master cylinder and its reservoir with brake fluid and bench-bleed the cylinder. With the cylinder balanced, hold your fingers over the brake line holes, press the piston with a large Phillips screwdriver while removing your finger from one hole, then place your finger back on the hole before releasing the piston. Repeat this multiple times and cap the holes afterward.

6

Install the new cylinder on the vehicle in reverse order of removal. Remove the caps on the holes and the brake lines before connecting the lines to the cylinder.

7

Bleed the braking system. Attach a clear tube to the bleeder valve on one brake caliper and open the valve as another person presses down on the brake pedal to remove air. Repeat this for all of the brakes and make sure the pedal feels firm and not spongy afterward.