The procedure used to remove air from the brake system is known as

• A. Purging
• B. Flushing
• C. Bleeding
• D. Ventilation

Answer: (C)

Air in a hydraulic brake system is compressible, so when you press the pedal the response becomes spongey and the brakes feel weak. The way to fix that is to bleed the system, which is the process of forcing brake fluid and any trapped air out of the lines through the bleed valves until only fluid remains in the circuits.

In practice, you open the bleed screws at the wheels and have someone press the brake, or use a pressure/bleed tool, while keeping the master cylinder reservoir topped up. You typically work from the wheel furthest from the master cylinder toward the closest, ensuring air doesn’t get drawn back in. You watch for a solid stream of fluid with no air bubbles; that indicates the air has been expelled and the system is bled and ready for service. For aircraft brakes, follow the approved bleeding procedure and sequence in the maintenance data to prevent any remaining air pockets in the hydraulic circuit.

Purging or flushing can involve renewing fluid or removing contaminants, but they’re not the standard terms for removing air from brake lines. Ventilation isn’t related to removing air from a hydraulic braking system.