When checking for air system leaks in a combination vehicle with brake applied, air loss should NOT be _________.

System Leak Check:
- Shut off the engine, chock your wheels, (if necessary), release the tractor protection valve and parking brake (push in), fully apply the foot brake and hold it for one minute.
- Check the air gauge to see if the air pressure drops more than 3 pounds in one minute (single vehicle) or 4 pounds in one minute (combination vehicle). After checking the brake with brake applied, release the foot brake and watch the gauges with brake unapplied for one minute.
- Check to see if the air pressure drops more than 2 pounds in one minute (single vehicle) or 3 pounds in one minute (combination vehicle).