During an air brake system test with the engine off, the allowable loss is:

During an air brake system test with the engine off, the allowable loss is:

• A. 3 psi in 1 minute
• B. 6 psi in 2 minutes
• C. 5 psi in 2 minutes
• D. 4 psi in 1 minute

Answer: (A)

Testing the air brake system with the engine off focuses on how much air pressure the system loses when the compressor isn’t replenishing it. After you fully charge the system, you leave the engine off and watch the pressure for one minute. The idea is to see whether there’s a leak that would cause the system to bleed down too quickly while you’re not adding air. The standard allowance is a loss of no more than 3 psi in one minute. This threshold helps catch meaningful leaks without overreacting to tiny, expected drops, ensuring the brakes will hold pressure during operation. If the pressure falls more than 3 psi in that minute, it signals a leak that needs repair before driving. Choices describing a larger loss or the test over a different time frame would not meet safety requirements.

Testing the air brake system with the engine off focuses on how much air pressure the system loses when the compressor isn’t replenishing it. After you fully charge the system, you leave the engine off and watch the pressure for one minute. The idea is to see whether there’s a leak that would cause the system to bleed down too quickly while you’re not adding air. The standard allowance is a loss of no more than 3 psi in one minute. This threshold helps catch meaningful leaks without overreacting to tiny, expected drops, ensuring the brakes will hold pressure during operation. If the pressure falls more than 3 psi in that minute, it signals a leak that needs repair before driving. Choices describing a larger loss or the test over a different time frame would not meet safety requirements.