In British Columbia, when you test the system air-loss rate of a bus or straight truck, the maximum acceptable leakage rate is 3 psi within
- 4 minutes.
- 1 minute. ✓
- 2 minutes.
- 3 minutes.
Answer: B. 1 minute.
The air-loss check is measured over a 1 minute hold, so 3 psi within 1 minute is the limit the test is looking for.
Why this is the answer
The handbook describes the leak test as a timed hold: with the engine off, you make a full brake application and hold it for one minute, then read how much pressure dropped. That is why any leakage figure is quoted against a one-minute window. The manual passage gives 4 p.s.i. per minute (6 p.s.i. with two trailers) as the limit, so the 3 p.s.i. number in the question is not the figure printed there; what the passage does confirm plainly is the one-minute test period.
Why the other answers are wrong
- A. 4 minutes. — Four minutes is far longer than the hold the handbook describes, which is a single minute before you read the gauge.
- C. 2 minutes. — Two minutes doubles the stated hold time, so the drop you read would not match the per-minute limit.
- D. 3 minutes. — Three minutes is not the period the manual gives for holding a full brake application while watching for air loss.
Remember it
Treat the leak check as a one-minute count: full pedal, hold, then read the gauge.