With a Buick brake master cylinder working properly, the hydraulic fluid can be compressed to the correct force to bring your vehicle to a safe and controlled stop. This is the part of your brake system that the input from the brake pedal is applied too. They are generally mounted on the upper portion of the firewall under the hood on the driver's side of the vehicle. There are two chambers in the brake master cylinder on your Buick. The smaller forward one is for the rear brakes and the larger aft one is used for the front brakes. The larger area and distance of the rear reservoir is how the brake bias is generated. This allows for a greater force to be applied to the front brakes which is desired for better control when stopping a vehicle. Before a brake master cylinder is placed on your Buick, it should first be bench bleed. This is the process for introducing the hydraulic fluid to the part. Once the brake master cylinder is mounted into place the entire brake system should then be bled. This process removes all of the air that might have become trapped within the system when it was apart. When bleeding the brake system the cover on the brake master cylinder should always remain on. If this is not done, hydraulic fluid will squirt from the reservoirs and get on other parts of your engine which will destroy the paint on your Buick. The Buick brake master cylinder is the heart and soul of your braking system. If it fails to perform and apply pressure to the brake lines, brake failure will occur. The only alternative for a drive to slow their car down is then to apply the manual parking brake or down shift to a lower gear.