Should you pump (keep pressing and releasing) air brakes?
- Yes, this procedure is recommended for highway driving.
- Yes, it helps build up air pressure.
- No, it causes loss of air pressure. ✓
- Yes, it compensates for poor adjustment of the brakes.
Answer: C. No, it causes loss of air pressure.
No — pumping the air brakes costs you air pressure, so you should not do it.
Why this is the answer
The handbook describes a service reservoir being drained or pumped down to zero, which shows that repeated pumping of the foot valve uses up the air stored in the system. Air pressure is what applies the brakes, so working the valve over and over draws the supply down instead of holding it steady. Nothing in these pages treats pumping as a technique to use while driving or as a way to build pressure back up.
Why the other answers are wrong
- A. Yes, this procedure is recommended for highway driving. — The handbook never presents pumping as a recommended highway driving procedure; it only mentions pressure being pumped down toward zero.
- B. Yes, it helps build up air pressure. — Pumping releases air rather than adding it, so it works against building pressure instead of raising it.
- D. Yes, it compensates for poor adjustment of the brakes. — The passages say nothing about pumping making up for badly adjusted brakes; the foot valve simply sends air pressure to apply the brakes.
Remember it
Think of the foot valve as spending air, not making it — each extra press draws the reservoir down.