Place some shop rags underneath the brake master cylinder to catch any spilled brake fluid, then remove the brake fluid from the reservoir. Unplug the electrical connector from the brake fluid level indicator and place some rags or newspapers under the brake line fittings. Using a flare-nut wrench, unscrew the brake line tube nuts and allow any residual fluid to drain onto the rags. Remove the brake master cylinder-to-power brake booster mounting nuts and remove the brake master cylinder from the engine compartment. If a new brake master cylinder is being installed, the power brake booster pushrod length must be checked and adjusted. Bench bleed the new brake master cylinder before installing it, attach a pair of brake master cylinder bleeder tubes to the outlet ports of the brake master cylinder, fill the reservoir with brake fluid, slowly push the pistons into the brake master cylinder, remove the bleed tubes, one at a time and install plugs in the open ports to prevent fluid leakage and air from entering, replace the O-ring seal on the brake master cylinder, thread the brake line fittings into the brake master cylinder, fill the brake master cylinder reservoir with fluid, then bleed the brake master cylinder and the brake system, have an assistant depress the brake pedal and hold the pedal to the floor, loosen the fitting just enough to allow air and fluid to escape then tighten it lightly, repeat this procedure on both fittings until the fluid is clear of air bubbles and then tighten the fittings securely, rinse the area under the brake master cylinder with clean water, fully tighten the mounting nuts, then the brake line fittings, tighten the brake master cylinder mounting nuts, and test the operation of the brake system carefully before placing the vehicle into normal service.