How should you check that the spring brakes come on automatically?

Step on and off the brake pedal (fan the brakes) with the engine off until the parking brake knob pops out.. Section 5.3: To check

How should you check that the spring brakes come on automatically?

ANSWER BREAKDOWN
  • A. Incorrect. "Drive until the tank is empty." is not correct. To check automatic application, fan the brakes to lower pressure. The parking brake knob should pop out when pressure drops to 20-45 psi.
  • B. Correct. To check automatic application, fan the brakes to lower pressure. The parking brake knob should pop out when pressure drops to 20-45 psi.
  • C. Incorrect. "Pull the knob out." is not correct. To check automatic application, fan the brakes to lower pressure. The parking brake knob should pop out when pressure drops to 20-45 psi.
  • D. Incorrect. "Drain the tanks manually." is not correct. To check automatic application, fan the brakes to lower pressure. The parking brake knob should pop out when pressure drops to 20-45 psi.