Pretrip Inspection and Daily Maintenance With the service brakes released, shut down the engine, wait one minute and note the air pressure gauge reading. Observe the air pressure drop in psi (kPa) per minute. Description Air Leakage in psi (kPa) Per Minute Released Applied Truck or Tractor Only 2 (14) 3 (21) Truck or Tractor w/Single Trailer 3 (21) 4 (28) Truck or Tractor w/Two Trailers 5 (35) 6 (42) Maximum Allowable Service Brakes Air Leakage Charge the air system until cutoff pressure of 125 psi (862 kPa) is reached. With the parking brakes released and the service brake applied, shut down the engine, wait one minute and note the air pressure gauge reading.
Observe the air pressure drop in psi (kPa) per minute. Table 9.1, Maximum Allowable Service Brakes Air Leakage If leakage exceeds the limits shown in Table 9.1 , repair all areas of leakage before driving the vehicle. 41. Test the parking brakes on a 20 percent grade. Pull the parking brake control valve knob or apply the hand brake with the vehicle on a 20 percent grade. If the parking brakes do not hold the vehicle, repair the parking brake system. WARNING Before operating the vehicle, be sure the spring parking brakes on the vehicle pass the above tests.
Otherwise an unexpected parking brake application could occur, causing some loss of vehicle control and possibly resulting in serious personal injury. 40. Test the service brakes before leaving the lot. When starting to move the vehicle and before pick- ing up speed, test the brakes with the foot valve and parking brake valve to be sure they will bring the vehicle to a safe stop. 9.22