|
Transportation Home
|
Procedure for Checking Air-Brake System Note: When performing your air-brake check, build air pressure to maximum (120-125) and check the following in order: Note: You have to have an open system to check the brakes. So release the parking brake before starting step one. 1. Check Air-Compressor Governor Cut in-out Pressure: The governor engages around 100 PSI and tops off around 120-125 PSI. Release the parking-brake, watch bus for any movement. The driver pumps the service pedal down to below 100 PSI. At this time the governor should be engaged and building air. Remember if you are building air the governor is working. Keep building air pressure until it tops off 120-125 PSI. 2. Test Air Leakage Rate With a fully charged air- system (typically 125 PSI) turn off the engine, turn key to battery. After the initial drop, time the air pressure drop. The loss rate should be no more than 2 PSI in one minute for single vehicles. Apply service brake pedal and hold for one minute. After the initial drop, the air pressure loss should be no more than 3 PSI in one minute for single vehicles. 3. Test Low Pressure Warning Signal: The driver keeps fanning off the air pressure by rapidly applying and releasing the service brake pedal. Light and buzzer should activate between 60-70 PSI. 4. Check that the Spring Brake comes on Automatically: Continue fanning off air pressure with the service brake pedal. At approx. 20-40 PSI, the spring brake valve should pop out. 5. Check Rate of Air Pressure Buildup: Start engine and with the engine at operating rpm (1,000- 1,500) the air pressure should build from 85-100 PSI within 45 seconds in a dual air system. 6. Test Parking Brake: With the parking brake applied, gently pull against it in a low gear to test that the parking brakes will hold. Simulate 5 mph, or 1,000 rpm if gauge is used. 7. Test Service Brakes: Release the parking brake, move the vehicle forward slowly (about 5 mph) and apply the brakes firmly using the service pedal. Do this 1 time. At this time you would check for any "pulling from side to side." |