What should be observed when performing the air pressure leakage test with brakes applied?

When performing an air pressure leakage test with the brakes applied, the primary focus is on monitoring the pressure drop over a specific time period, typically one minute. This is crucial because it helps determine the integrity of the air brake system.

A constant gauge reading indicates that there is no significant air loss, which is a desirable outcome, but the specific practice outlined in the test is to actively monitor for any pressure drop within the designated time frame. If the pressure remains constant throughout this minute, it implies that the system is functioning properly. Therefore, monitoring the pressure drop gives a clear indication of how well the air brake system is sealed, identifying any leaks that could compromise safety.

This test is standard practice to ensure that the brakes are reliable and effective, which is vital for safe vehicle operation.