GM Century/Lumina/Grand Prix/Intrigue 1997-2000

Brake Master Cylinder


The brake master cylinder is designed for use in diagonally split hydraulic systems. It incorporates the functions of the standard dual master cylinder plus a fluid level sensor and integral proportioner valves. In a diagonally split system, the left rear brake and the right front brake are on the same hydraulic circuit in the master cylinder, and the left front brake and the right front brake on the other circuit.

The master cylinder is equipped with a fluid level sensor switch located in the side of the reservoir. The switch activates the BRAKE warning lamp if the fluid level is low. Once the fluid level is corrected, the BRAKE warning lamp will go out.


The brake system in these vehicles is a complex system dependent on absolutely clean brake fluid of the proper type. Use only SUPREME 11 or equivalent DOT 3 brake fluid from a clean, sealed container. Do not use fluid from an open container that may be contaminated with water. Using the wrong fluid or contaminated fluid could result in damage to expensive components, or loss of braking, with possible personal injury.

Avoid spilling brake fluid on any of the vehicle's painted surfaces, wiring cables or electrical connectors. Brake fluid will damage paint and electrical connections. If any fluid is spilled on the vehicle, flush the area with water to lessen damage.

Do not use power steering or transmission fluid in the brake system. Do not reuse brake fluid accumulated during brake system bleeding. Always store brake fluid in a closed container. Reseal brake fluid containers immediately after use. Do not use brake fluid left in an open or improperly sealed container, because it absorbs moisture, or can become contaminated.

Click image to see an enlarged view

Fig. Pay attention to the brake fluid specification on the fluid reservoir cap. Use DOT 3 brake fluid only, NEVER silicone fluid or any other type of oil


The brake hydraulic system is a closed system. Low levels of fluid may indicate a need for service as there may be a leak in the system. It is good practice to check the brake fluid level during oil changes or whenever under the hood.

Overfilling the reservoir must be avoided due to the potential for overflow onto the nearby catalytic converters in the exhaust system. Brake fluid is flammable, and contact with hot exhaust components could result in a fire and possible personal injury.

The master cylinder reservoir is on the master cylinder and is located under the hood on the driver's side of the vehicle. The master cylinder reservoir contains enough fluid so that it never needs service under normal conditions. A low fluid level sensor in the master cylinder reservoir will warn of low fluid level, which could indicate a leak.

Click image to see an enlarged view

Fig. Remove the brake master cylinder reservoir cap . . .

Click image to see an enlarged view

Fig. . . . then check the fluid level against the marks on the neck of the reservoir

Click image to see an enlarged view

Fig. When adding brake fluid, use only DOT 3 brake fluid from a clean, fresh, sealed container

Thoroughly clean the reservoir cap before removal to avoid getting dirt in the reservoir. Remove the twist cap and diaphragm under the cap. The fluid level should be at the MAX fill mark on the reservoir when full. Reinstall the cap and diaphragm assembly when the reservoir is full.