Brake Master Cylinder: Testing and Inspection

Be sure that the master cylinder compensates in both parts. This can be done by applying the brake pedal lightly (engine running with power brakes) and observing for brake fluid squirting up in the reservoirs. This may only occur in the front chamber. To determine if the rear compensating port is open, pump up the brakes rapidly and hold the pedal down. Have an observer watch the fluid in the rear reservoir while the pedal is raised. A disturbance in the fluid indicates that the compensating port is open.