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BC Class 1–4: Air brake pre-trip test

The air brake pre-trip on the road test: draining reservoirs, governor cut-out and cut-in, low-air warning, trailer supply valve closing, build-up time and leakage limits.

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Air brake pre-trip test · Question 1Score 0/0

For a single-unit truck, what air loss is allowed during the one-minute leakage test?

Study reference: Driving Commercial Vehicles (ICBC, 2024 edition), Ch. 10 Vehicle and air brake pre-trip inspections — Air brake system tests, Leakage test

All 11 questions in this test

Every question and its answer choices. The correct answers and explanations appear when you take the test above.

  1. For a single-unit truck, what air loss is allowed during the one-minute leakage test?

    1. 6 p.s.i. per minute
    2. 1 p.s.i. per minute
    3. 4 p.s.i. per minute
    4. 3 p.s.i. per minute

  2. What application pressure is held during the leakage test?

    1. 90 to 100 p.s.i. for one minute
    2. Full pressure for ten minutes
    3. 20 p.s.i. for five minutes
    4. 60 p.s.i. for 30 seconds

  3. Why do the leakage test with the parking brakes released?

    1. To check the low-air warning
    2. To avoid compounding
    3. To save fuel
    4. To hear the compressor

  4. At what pressure should the low-air warning come on during the pump-down?

    1. Exactly 80 p.s.i.
    2. At or below 40 p.s.i.
    3. At or above 60 p.s.i.
    4. At 20 p.s.i.

  5. In the Class 1 pump-down, when must the trailer air supply valve close?

    1. When pressure reaches 80 p.s.i.
    2. When the highest tank reads 20–45 p.s.i.
    3. Only when the engine is shut off
    4. As soon as any gauge drops to 60 p.s.i.

  6. During the pump-down, before what pressure must the governor cut in?

    1. 100 p.s.i.
    2. 80 p.s.i.
    3. 45 p.s.i.
    4. 60 p.s.i.

  7. How should you treat the vehicle's history for the pre-trip test?

    1. Assume it has not been driven that day
    2. Assume it was inspected this morning
    3. Skip items a mechanic has signed off
    4. Assume the brakes were adjusted yesterday

  8. Which reservoir must be drained on the road test?

    1. The secondary reservoir only
    2. The trailer reservoir only
    3. None; draining is optional
    4. The supply (wet) reservoir

  9. Between what pressures must the governor stop the compressor pumping?

    1. 90 and 100 p.s.i.
    2. 60 and 80 p.s.i.
    3. 135 and 150 p.s.i.
    4. 105 and 135 p.s.i.

  10. You have automatic slack adjusters on the road test. What must you show the examiner?

    1. How to reset the ABS
    2. How to replace a brake chamber at the roadside
    3. How manual slack adjusters are adjusted
    4. Nothing about adjustment

  11. You drain only the supply reservoir and the primary gauge also drops. What might be faulty?

    1. A one-way check valve
    2. The safety valve
    3. The governor
    4. The foot valve

Air brake pre-trip test: key rules to remember

Our summary of what the official handbook says on this topic, in our own words. Read it before or after the practice questions above, then check the original chapter. Read the official chapter ↗

Air brake pre-trip test requirements (p. 199, 203)

  • Commercial and heavy trailer applicants do a pre-trip inspection on the road test; if the vehicle has air brakes, or for an air brake endorsement, you also inspect the air brake system.
  • With manual slack adjusters you must show you can adjust a brake; with automatic slack adjusters you must explain how manual adjusters are adjusted.
  • Air-brake-endorsement-only applicants complete just the air brake pre-trip (the red-coded portions of the Class 1 and 3 inspections).
  • On the test, assume the vehicle has not been driven that day; point to or touch each item and say what you are checking for.

Under hood and in cab (p. 205–208, 215–217)

  • Drain the reservoirs; for the road test only the supply reservoir must be drained, but all reservoirs should be drained daily.
  • Watching the gauges while draining helps tell the supply reservoir from the primary and secondary.
  • Check the compressor is securely mounted and its lines have no kinks, leaks, cuts or abrasions; check belt tension.
  • After draining only the supply reservoir, if the primary or secondary gauges also lost pressure, a one-way check valve may not be working.
  • Check that the compressor stops pumping (governor cut-out) between 105 and 135 p.s.i. (724 and 931 kPa).

Air brake system test, single unit (Class 3) (p. 218)

  • Pump the brake pedal down to about 80 per cent of maximum (100 p.s.i. if maximum is 125) and confirm pressure starts to build (governor cut-in); cut-in must happen before pressure falls below 80 p.s.i. (552 kPa).
  • Pump down further and check the low-air warning comes on at or above 60 p.s.i. (414 kPa).
  • Pump down below 50 p.s.i., then check pressure rebuilds from 50 to 90 p.s.i. (345 to 620 kPa) within three minutes at fast idle (1,000 to 1,200 r.p.m.).
  • Release the spring parking brakes if they applied during the pump-down.
  • In some systems one service reservoir fills first and the other starts at about 85 to 95 p.s.i.; either way, 50 to 90 p.s.i. must take no more than three minutes.

Air brake system test, tractor-trailer (Class 1) (p. 208)

  • After governor cut-in and low-air checks, keep pumping down and check the trailer air supply valve closes when the highest reservoir gauge reads 20 to 45 p.s.i. (138 to 310 kPa); the parking brake valve may or may not also close.
  • Shut off the engine and confirm the trailer brakes have applied.
  • Disconnect both glad hands and check no air escapes from the tractor or trailer through them.
  • Make a foot brake application and listen that no air escapes through the supply or control line.
  • Reconnect, check the electrical connection and that lines have enough slack for turns and are not chafing, then check the 50-to-90 p.s.i. build-up within three minutes.

Leakage test (p. 213, 221)

  • Do the leakage test with the engine off so you can hear leaks, air at least 100 p.s.i. and parking brakes released (to avoid compounding).
  • Make a full application of 90 to 100 p.s.i. (620 to 690 kPa) and hold it one minute.
  • Single-unit truck: after the initial drop, loss must not exceed 3 p.s.i. (20.7 kPa) per minute.
  • Tractor and one trailer: no more than 4 p.s.i. (27.6 kPa) per minute; with two trailers, no more than 6 p.s.i. (41.4 kPa) per minute.
  • There must be no audible air leaks.

Brake response, tug and steering tests (p. 213, 221, 228)

  • Single unit: in low gear gently tug against the parking brakes (they must hold), release, roll ahead slowly and apply the foot brake, then check steering wheel play.
  • Check brake adjustment while underneath the vehicle; check foundation brakes, chambers, slack adjusters, s-cams, drums, linings and air lines at each wheel.
  • Check that brake chamber mounting and clamps are secure, no cracks, corrosion or holes, and no audible leaks.
  • Check drums are not cracked and linings or drums are not contaminated with oil or grease.

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