When the driver releases the foot valve treadle in a vehicle without quick release valves, where would the application/service air from the brake chambers go?
- To the relay emergency valve
- To the nearest service reservoir
- Back to the foot valve to be exhausted into the atmosphere ✓
- To the hand valve
Answer: C. Back to the foot valve to be exhausted into the atmosphere
The air goes back through the line to the foot valve and is released through its exhaust port into the atmosphere.
Why this is the answer
The handbook explains that without a quick release valve, releasing the brakes sends all the air in the lines and brake chambers back through the foot valve exhaust port. The foot valve is the device that lets application air out to the atmosphere when you take your foot off the treadle. With a quick release valve, only the small line volume vents at the foot valve while most chamber air vents near the chambers; the question asks about a vehicle without one, so the air returns to the foot valve.
Why the other answers are wrong
- A. To the relay emergency valve — The relay emergency valve is not described as the place where released application air from the chambers is exhausted.
- B. To the nearest service reservoir — The released air is vented to the atmosphere, not sent back into a service reservoir.
- D. To the hand valve — The hand valve is not described as receiving or exhausting this released application air; the foot valve does that.
Remember it
If there is no quick release valve near the chambers, picture the air traveling back to the pedal to escape.