Maximum leak rate per minute with engine off and brakes released?

• A. 4 psi per minute
• B. 3 psi per minute
• C. 2 psi per minute
• D. 1 psi per minute

Answer: (C)

The main idea tested is how much air pressure the brake system can lose in a short, idle state to show the integrity of the system. When the engine is off and the brakes are released, the system should hold pressure with only a tiny drop in one minute. A maximum loss of 2 psi per minute means the leaks are minor and acceptable for a safe, functioning system. If the pressure falls faster than that, it signals leaks in hoses, fittings, valves, or other components that need repair before driving. This test is done after building pressure to around 120–140 psi, then observing for one minute with the brakes released to determine if the leak rate stays at or below the 2 psi per minute threshold.