Malfunction Recognition and Emergency Response
Domain 6 tests recognition of failures and the safe response. The Georgia air brake exam wants you to identify low pressure, leaks, compressor or governor failure, brake fade, pulling, frozen lines, and spring brake problems, then choose a response that gets the vehicle off the road without losing control.
Recognition and response
- Low-pressure warning or rapid gauge drop: stop safely. Downshift, use engine braking, apply service brakes if available, and move off the road. Spring brakes will apply at 20-45 psi. Do not pump the brakes.
- Audible leak, failed build test, or a compressor that will not build: do not continue. A governor stuck open can overpressure and vent at the safety valve; a failed compressor causes pressure to fall.
- Brake fade from overheating: use a lower gear and stop to cool. Pulling or grabbing: suspect contaminated linings, a stuck slack adjuster, or unequal adjustment; inspect. Frozen air lines: use the air dryer or alcohol evaporator; do not use an open flame.
- Spring brakes that will not release: check pressure and valves; do not cage the brakes and drive. On a grade, use an escape ramp if stopping distance is uncertain.
Worked example
The low-pressure buzzer sounds and the gauge falls to 40 psi on a mountain grade. The driver should not fan the brakes. Instead, downshift, apply the service brake steadily, and steer for a pullout or escape ramp. If pressure continues to fall, the spring brakes will apply at 20-45 psi and stop the vehicle. Continuing to the bottom because the brakes still feel partly effective is the dangerous choice.
Traps that cost marks
Pumping the brakes when pressure is low speeds the loss of air. Caging a spring brake to keep driving hides a failure. Ignoring a warning that comes on intermittently can lead to a total loss. Using water on overheated brakes can crack drums. Do not assume a pulling brake will cure itself; it may be a leaking chamber or contaminated lining.
Key points
- Low pressure: stop safely and do not pump the brakes.
- Spring brakes apply automatically at 20-45 psi.
- Brake fade requires cooling and a lower gear.
- Do not cage a spring brake to keep driving.
- Use an escape ramp if you cannot stop safely on a grade.