GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

Brake Master Cylinder


See Figure 1

The vehicles covered in this information are equipped with a dual braking system, allowing a car to be brought to a safe stop in the event of failure in either the front or rear brakes. The dual master cylinder has two separate reservoirs, one connected to the front brakes and the other connected to the rear brakes. In the event of failure in either portion, the remaining portion is unaffected.

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Fig. Fig. 1: The dual brake master cylinder has two separate reservoirs


Use only heavy duty brake fluid meeting DOT 3 specifications. Using any other type of fluid may result in severe brake system damage.

Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded. Also, do not allow any brake fluid to come in contact with a painted surface; it will damage the paint.


See Figure 2

If should be obvious how important the brake system is to safe operation of your vehicle. The brake fluid is key to the proper operation of your vehicle. Low levels of fluid indicate a need for service (there may a leak in the system or the brake pads may just be worn and in need of replacement). In any case, the brake fluid level should be inspected at least during every oil change, but more often is desirable. Every time you open the hood is a good time to glance at the master cylinder reservoir.

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Fig. Fig. 2: When adding brake fluid to the master cylinder, use only clean, fresh fluid from a sealed container

To check the fluid level on most vehicles covered by this information, you may peer through the side wall of the reservoir and observe the level in relation to the markings. If the reservoir is opaque, simply unsnap and lift off the reservoir cover, to check the fluid level; it should be within 1 /4inch (20-26mm) of the tops of the reservoir walls. When making additions of brake fluid, use only fresh, uncontaminated brake fluid which meets or exceeds DOT-3 standards. Be careful not to spill any brake fluid on painted surfaces, as it will quickly eat the paint. Do not allow the brake fluid container or the master cylinder to remain open any longer than necessary; brake fluid absorbs moisture from the air, reducing the fluid's effectiveness and causing corrosion in the lines.