GM Service Manual Online
For 1990-2009 cars only

Caution: Refer to Brake Fluid Irritant Caution in the Preface section.

Caution: Refer to Brake Fluid Caution in the Preface section.

Notice: Refer to Filling the Master Cylinder Notice in the Preface section.

Notice: Refer to Brake Fluid Damage to Electrical Connections Notice in the Preface section.

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in the Preface section.

Notice: Refer to Clutch Hydraulic System Lubricant Notice in the Preface section.

Notice: Refer to Using Proper Power Steering Fluid Notice in the Preface section.

Brake fluid should meet the DOT-3 specification. Use only clear fluid from a sealed container. Fluid that is exposed to the air will absorb moisture. Water in the brake fluid will cause the fluid to boil and the rubber components to deteriorate. Thoroughly clean the master cylinder reservoir cap before removing it. Do not let any dirt or foreign material fall into the fluid reservoir. There is a brake fluid level sensor under the master cylinder reservoir. This brake system uses a BRAKE warning lamp in the instrument panel cluster. When the ignition switch is in the START position, the BRAKE warning lamp should go off when the ignition switch returns to the ON position. The following conditions will active the BRAKE warning lamp:

    • The lamp should be on whenever the parking brake is applied and the ignition switch is in the ON position.
    • A low fluid level in the master cylinder will turn the BRAKE lamp on.

The correct brake fluid level is marked on the both side of the brake fluid reservoir. If the fluid level is below the MIN indicator mark, check the hydraulic brake system for leaks. Fix any leaks. Then refill the reservoir to the MAX indicator mark

Master Cylinder

Notice: Do not use lubricated compressed air on brake parts as damage to rubber components may result.

Important: 

   • Replace all the components included in the repair kits used to service the master cylinder.
   • Lubricate the rubber parts with clean brake fluid to ease assembly.
   • If any hydraulic component is removed or disconnected, it may be necessary to bleed all or part of the brake system. Refer to Hydraulic Brake System Bleeding .
   • The torque values specified are for dry, unlubricated fasteners.
   • Perform all service operations on a clean bench, free from all traces of mineral oil.

The master cylinder is designed for use in a diagnonally split system. One front and one diagonally opposite rear brakes are served by the primary piston. The opposite front and rear brakes are served by the secondary piston.

The master cylinder incorporates the functions of the standard dual master cylinder, plus a low fluid level indicator and the proportioning valves in the non-antilock braking system. The proportioning valves limit the outlet pressure to the rear brakes after a predetermined master cylinder pressure has been reached. The brake master cylinder sensor is attached under the body of the plastic brake master cylinder reservoir.

Fluid Level Sensor

The master cylinder is equipped with a fluid level sensor. This sensor will activate the BRAKE light if a low fluid level condition is detected. Once the fluid level is corrected, the BRAKE light will go out.