To test the static air leakage rate, you should

To test the static air leakage rate, you should

• A. Turn off the engine, release the parking brake, and let the engine settle
• B. Increase engine speed and watch the gauge
• C. Drain the air tanks completely
• D. Keep the engine running and park safely

Answer: (A)

Static air leakage is measured when the system is not being charged and the brakes aren’t holding pressure. To do this correctly, turn off the engine, release the parking brake, and let the system settle for about a minute. With the engine off, the compressor isn’t recharging the tanks, and releasing the parking brake ensures you’re not testing leakage caused by the brake valves or parking brake. If the pressure drops more than the allowed amount during that minute, there’s a leak somewhere in the system. If you instead increase engine speed, drain the air tanks, or keep the engine running and park, you’d be testing charging rate or other conditions, not the static leakage rate, so those options don’t reflect the true static leakage.

Static air leakage is measured when the system is not being charged and the brakes aren’t holding pressure. To do this correctly, turn off the engine, release the parking brake, and let the system settle for about a minute. With the engine off, the compressor isn’t recharging the tanks, and releasing the parking brake ensures you’re not testing leakage caused by the brake valves or parking brake. If the pressure drops more than the allowed amount during that minute, there’s a leak somewhere in the system. If you instead increase engine speed, drain the air tanks, or keep the engine running and park, you’d be testing charging rate or other conditions, not the static leakage rate, so those options don’t reflect the true static leakage.