How to Replace the Brake Master Cylinder in a 1993 Pontiac Bonneville

The brake master cylinder in a 1993 Pontiac Bonneville stores the brake fluid until the pedal and booster send the fluid to the brakes. The Bonneville does have a few added options, such as a brake fluid level sensor, which you must deal with. Other than that, the installation of the cylinder is very much like other vehicles. If you need to replace the master cylinder, this procedure will force air into the brake system that you will need to take care of.

Instructions

Removal

1

Disconnect the negative battery cable with a wrench then disconnect the electrical connector on the master cylinder reservoir for the fluid level sensor.

2

Place shop rags on the ground directly beneath the line fittings for the cylinder then remove the fittings at the cylinder with a flare-nut wrench and disconnect the lines. Plug the lines with rubber plugs.

3

Unscrew the mounting nuts located at the end of the cylinder where it connects to the brake booster and remove the cylinder.

4

Pry the reservoir off the cylinder with a flat head screwdriver.

Installation

5

Fasten the reservoir to the top of the replacement cylinder, making sure there are new grommets on the mounting holes.

6

Connect the cylinder to the brake booster and apply the two mounting nuts with the wrench.

7

Reconnect the brake lines to the cylinder onto their fittings with the flare-nut wrench then reconnect the electrical connector to the reservoir and connect the battery cable.

8

Fill the brake master cylinder to the full mark with fresh brake fluid.

9

Raise the rear of the car, support it on jack stands and remove the wheels. Connect a rubber tube to the bleeder valve on one rear wheel's brake caliper and submerge the tube in a small bottle/container partially filled with fluid.

10

Loosen the caliper bleed valve as an assistant presses the pedal; air and fluid will come out of the tube. Close the valve, release the pedal and repeat until there are no air bubbles.

11

Repeat Steps 5 and 6 for the other rear wheel, then remount the rear wheels and lower the car off the jack stands. Raise the front end on the jack stands, remove the front wheels and bleed those brakes.

12

Remount the front wheels, lower the car and fill the reservoir if necessary.