The Air Brake system plays the most important function that being safely stopping the vehicle. Because of the importance of the air brake system it is vital that you know your brake system working components and stay focused each time you conduct any inspection. Remember safety first not only for yourself but for everyone on the roadways.
CDL Air Brakes – 7 – Seven Step Check
The Seven-Step Air Brake check is designed to test the governor cut-in and cut-out pressures, air pressure leakage, warning buzzer, brake valves and the air pressure rebuild rates.
Brakes off means the yellow and/or red valve is pushed in (on = valve out).
- Engine on / Brakes on – check gauges to make sure governor cuts compressor off at 120 psi. Pump brakes until the pressure drops below 100 psi to make sure governor cuts compressor on.
- Engine off / Brakes off – do not touch brakes – watch gauges to make sure pressure does not drop more than 3 psi in one minute.
- Press and hold brake pedal – watch gauges to make sure pressure does not drop more than 4 psi in one minute.
- Turn- key on / Engine off / Brakes off – pump brake until the pressure drops to 60 psi – warning buzzer should sound at or before 60 psi. continue pumping brakes until reaching 20 to 40 psi – Emergency (red) and Service (yellow) brake valves should pop out turning brakes on.
- Rebuild air pressure in the tank – hold accelerator at 1500 RPM. Watch air gauges and notice that pressure rate of build between 85 psi and 100 psi should not take more than 45 seconds.
- Perform tug tests. Tug against Parking Brake only. Tug against Emergency
Brake only. Tug against Hand Brake only. Test service brake by accelerating to 5mph and pressing the brake pedal. If the vehicle pulls to one side, this indicates a brake alignment problem.
If there is a problem discovered while testing the Air Brakes, do not drive the vehicle. It is your responsibility to make sure it is repaired by a mechanic. Never operate a vehicle that is unsafe to drive.