Testing

Vacuum Leak Test

1. Park the vehicle on a level surface. Place the vehicle in PARK (automatic) or REVERSE (manual) with the engine OFF, and apply the parking brake. Chock the rear wheels to prevent vehicle movement.

   Note: Wheel chocks may be purchased at your local auto parts store, or a block of wood cut into wedges may be used.

2. Start the vehicle and operate the engine at idle without touching the brake pedal for at least one minute.

   Note: For manual transmission vehicles, place the vehicle in NEUTRAL with the parking brake applied.

3. Turn off the engine and wait one minute.
4. Test for the presence of assist vacuum by depressing the brake pedal and releasing it several times. If vacuum is present in the system, light application will produce less and less pedal travel. If there is no vacuum, there is a leak allowing air into the system.

System Operation Test

1. With the engine OFF, pump the brake pedal until the vacuum supply is entirely gone.
2. Place your foot on the brake pedal and apply steady pressure. Maintain steady pressure on the brake pedal.
3. Start the engine and let it idle. If the system is operating correctly, the brake pedal should fall to the floor.

Note: Power brake systems may be tested for hydraulic leaks just as ordinary systems are tested.

WARNING
Never use brake fluid from an open container. Brake fluid is hydroscopic, and will absorb moisture that will compromise the efficiency of the fluid. Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy brake fluid recommended for your vehicle and brake system. Never mix DOT grade brake fluid with Silicon Brake Fluid; the combination is tantamount to adding air to the brake lines, causing weak and ineffective braking and an expensive procedure to clean, flush and replenish the brake system. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Discard any brake fluid that is removed from the system. Also, vehicles equipped with ABS (Antilock Brake Systems) must be professionally bled using a pressure bleeder or a gravity bleed procedure. Refer to a qualified repair center for service.