A ______ ______ valve is designed to prevent a complete loss of hydraulic system fluid if a brake line fails or leaks.

• A. Debooster valve
• B. Pressure relief valve
• C. Check valve
• D. Lockout Debooster valve

Answer: (D)

In a multi-line hydraulic brake system, protecting the entire system from a single line failure is crucial. A lockout debooster valve is designed to isolate a suspect brake line by locking out the debooster function and closing the path to that line. This prevents hydraulic fluid from being pumped out through the leaking line, helping preserve the remaining fluid in the system and keeping other braking circuits operable. In short, it provides a conditional shutoff that stops a total fluid loss when a brake line fails. Other valves either regulate pressure, prevent backflow, or adjust boosting without isolating a leaking line, so they don’t offer the same protection against complete fluid loss.