Air Brake Mock

#1. When must you chock the wheels of your stopped vehicle?

(c) If you'll be more than 50 metres from your vehicle

(b) If the parking brake isn't set

(b) or (c)

(a) At all times

Before proceeding with your pre-trip inspection, you must chock the wheels and make sure the chocks will keep your vehicle from moving. This is especially important for vehicles equipped with air brakes, because some tests of the air brake system require the parking brakes to be released.

#2. How often should the air tanks be drained?

During periodic maintenance

Monthly

Daily

Weekly

Moisture that accumulates in the air tanks can freeze overnight, and the ice can stop air brake valves from working properly. To prevent this, drain the air tanks at the end of each workday

#3. When you test the system air-loss rate, the maximum acceptable leakage rates per minute for a straight truck, a tractor pulling one trailer, and a tractor pulling two trailers are

4, 4, 6 psi respectively.

2, 3, 9 psi respectively.

3, 4, 6 psi respectively.

1, 2, 3 psi respectively.

In British Columbia, the maximum acceptable leakage rates per minute are 28 kPa (4 psi) for single vehicles (buses, straight trucks and bobtail tractors) and tractor-trailers with one trailer, and 41 kPa (6 psi) for tractor-trailers with two trailers. If the leakage rate is higher, check for leaks and correct them.

#4. Which of the following is NOT a part of a truck's braking system?

Rotor

Wedge

V-brake

S-cam

V-brakes are typically used in bicycles.

#5. Should you pump (keep pressing and releasing) air brakes?

No, it causes loss of air pressure.

Yes, it helps build up air pressure.

Yes, it compensates for poor adjustment of the brakes.

Yes, this procedure is recommended for highway driving.

Each time you release the brakes, some compressed air leaves the system and must be replenished by the air compressor. If you keep pressing and releasing the brake pedal, air may leave the system faster than the air compressor can replenish it. The air pressure may drop to the point that the low air pressure warning signal will come on.

#6. What does caging a brake chamber do?

It adjusts the brake.

It increases braking power.

It disables the service brake.

It disables the spring brake.

If your vehicle’s service brakes fail, the emergency (spring) brakes will activate and stop your vehicle. Then to tow your vehicle for repairs, it will be necessary to disable the spring brakes. A technician can manually compress or “cage” the spring in each spring brake chamber. Obviously the vehicle will be undrivable at this point because it will have no working brakes at all.

#7. Brake fade can lead to

total loss of braking capability.

loss of compressed air.

tire blowout.

Opening of the safety valve.

If the conditions that are causing service brake fade (loss of braking effectiveness) are not corrected, the brakes may continue fading until they can’t slow your vehicle at all.

#8. An application pressure gauge shows the air pressure

at which the air compressor will cut in.

that has been used during the trip.

in the tanks.

being applied to the brakes.

If your vehicle is so equipped, the application pressure gauge will show how much air pressure you are applying to the brakes. If you have to apply more pressure than before to achieve the same braking effect, it means your brakes are fading (becoming less effective).

#9. Which of the following is an advantage of wedge brakes over S-cam drum brakes?

More braking power

Simpler design

Installed on more commercial vehicles

No exposed linkage

In a wedge braking system, the brake chamber directly faces the brake drum. Compared with S-cam drum brakes, wedge brakes lack the exposed linkage of the pushrod, clevis pin and external slack adjuster. (Most wedge brakes have internal automatic adjusters.) Today, most commercial vehicles have disc brakes or S-cam drum brakes. However, wedge brakes are still favored for some military and other applications for which the lack of exposed linkage is advantageous on rough, corrosive, or dangerous ground.

#10. If you're using the applied stroke method during your pre-trip inspection, pushrod travel must not exceed

2¼ inches.

1½ inches.

1¾ inches.

1¼ inches.

If you’re using the applied stroke method, you must adjust the brake if pushrod travel is more than 1¾ inches (45 mm)

#11. While travelling downhill, you notice that each time you want to brake, you must press the brake pedal farther down than the last time to achieve the same braking force. What could be causing this?

A jammed foot brake pedal

Brake fade

A too-slow air compressor

A faulty air compressor governor

Brake fade is the reduction in braking effectiveness that can occur after repeated or continuous application of the brakes. You may find that you have to press the brake pedal farther down to achieve the same amount of braking force that you did before.

#12. Which statement is true of spring brakes?

They are not as strong as service brakes.

They are as strong as service brakes.

They are stronger than service brakes.

They can be used in lieu of service brakes.

Spring brakes start to drag as pressure drops to 60 psi, and they release as pressure rises to 60 psi. Yet a full service brake application can be 100 psi. The coil spring in most spring parking brake chambers can exert a force of between 1,500 and 2,000 pounds. With a service brake application of 100 psi, a typical Type 30 brake chamber can produce a force of 30 × 100 = 3,000 pounds.

#13. After you've connected your tractor to a trailer, you should test the trailer service brakes by applying

The trailer air supply valve.

The hand control valve.

The parking brake control valve.

The treadle (foot) valve.

After connecting your tractor to the trailer, test the action of the trailer service brakes by applying the hand control valve. This valve applies only the trailer service brakes, not the tractor service brakes. For this reason, the trailer hand valve should not be used for normal braking once your vehicle is on the road.

#14. Air compressors can either be driven by the engine belt and pulleys or

mounted on the differential.

mounted on the front axle.

inbuilt with the engine block and driven by gears.

in none of the above locations.

Air compressors used to be driven by the engine belt and pulleys. But today’s modern air compressors are mounted directly on the engine and driven by gears. Some models are even lubricated with the engine’s oil supply

#15. If you find a major defect in the air brake system, you should

Note the defect in your logbook and complete your trip.

Not drive the vehicle until the defect is repaired.

Ignore it.

Complete your trip and inform the operator.

Under British Columbia Motor Vehicle Act Regulation 26/58, it is an offence to knowingly drive a vehicle with defective brakes.

#16. Which brakes are more powerful, the spring brakes or the service brakes?

The service brakes are more powerful.

It depends on the make and model of the vehicle.

The spring brakes are more powerful.

The spring brakes and service brakes are equally powerful.

The spring brakes activate only if air pressure has fallen to the point that service brake operation is impaired. Many vehicles can still be driven even with the spring brakes applied because they have less braking power than the service brakes

#17. On a tractor-trailer, if the supply and service lines to the trailer are cross-connected, what may happen?

The tractor may lose compressed air.

The trailer parking brakes may not release.

All of the above may happen.

The service brakes will not work.

If you cross-connect the air lines, supply air will be sent to the trailer service line instead of the trailer air tanks. Tank air will not be available to release the trailer spring brakes (parking brakes). And when you press the brake pedal, service air won’t flow to the trailer brake chambers, so the service brakes won’t work either.

#18. To check the brake chambers for leaks, you should

Release the service brakes and apply the parking brakes.

Cover each brake chamber in soapy water.

Start the engine.

Release the parking brakes and apply the service brakes.

Each air brake chamber with a spring brake is like two chambers in one: the usual service brake chamber and a spring brake chamber attached to the rear of the service brake chamber. To test for leaks, you need to fill both of these with air. To fill the spring brake chambers, release the parking brakes by pulling out the yellow button on the dashboard. To fill the service brake chambers, press and hold the brake pedal. Then listen for the hiss of escaping air and check the rate of air loss

#19. The air compressor should be inspected only when

The vehicle is parked on a level surface.

The engine is idling.

The engine is off.

The parking brakes are released.

To check whether the air compressor is properly mounted and secure, you may need to touch it (and its engine belt, if it’s belt driven). The air compressor runs whenever the engine is on. It produces compressed air at a temperature of about 200 °C (about 400 °F). Therefore, it’s safest to turn off the engine so the air compressor and any belts are off as well.

#20. Your vehicle passes the tug test of the parking brakes if

the front wheels are blocked.

the vehicle moves only slightly back and forth.

the wheels only turn a half revolution.

the truck moves 1.5 metres or less.

To perform a tug test, first make sure that the engine is on, the transmission is in a low gear, and the parking brakes are set. Then try to pull forward. The parking brakes should prevent the vehicle from doing more than just slightly rocking back and forth. If you see the wheels actually roll, it means the vehicle has failed the tug test. This counts as a major defect. The vehicle cannot be legally driven on the road until this defect is repaired.

#21. As air pressure builds during your pre-trip inspection of the air brakes, the low air pressure warning device should deactivate at

70 psi.

80 psi.

50 psi.

60 psi.

The low air pressure warning device must activate when pressure falls to 60 psi (414 kPa) and deactivate when pressure rises to the same level – 60 psi (414 kPa). However, it activates at even higher pressures in some vehicles.

#22. What are the main components of a simple, basic air brake system?

Air lines, foundation brakes, governor, reservoir, spring brake modulator

Air lines, foot valve, foundation brakes, relay valve, reservoir

Air lines, compressor, foot valve, foundation brakes, governor, reservoir

Air lines, compressor, foot valve

The necessary components of the simplest possible air brake system are as follows: (a) a compressor to pump air; (b) a governor to control the compressor; (c) air lines to allow the pressurized air to flow between the air brake system components; (d) a reservoir to store the compressed air; (e) a foot valve that sends compressed air from the reservoir to the brakes when you press the brake pedal; and (f) the foundation brakes, one at each wheel.

#23. The effectiveness of the spring brakes for emergencies or parking

can only be tested by brake service specialists.

depends on the adjustment of the service brakes.

increases as heat increases in the brakes.

is not affected by the adjustment of the service brakes.

The effectiveness of a vehicle’s spring brakes depends on the condition of the brakes and proper brake adjustment. If the brakes are out of adjustment (for example, the pushrod stroke is excessive), neither the service brakes nor the spring brakes may work properly.

#24. How should you test your vehicle's low air pressure warning signal?

Manually let the air out of your brakes and see if the signal comes on.

Repeatedly press and release the brake pedal to lower the air pressure to 414 kPa (60 psi).

Pump the brakes while your ignition is off.

Repeatedly press and release the brake pedal to lower the air pressure to 207 kPa (30 psi).

Start the test with the pressure above 621 kPa (90 psi) and the ignition on. Then repeatedly press and release the brake pedal. In most vehicles, the low air pressure warning signal should come on when the pressure falls below 414 kPa (60 psi). If the warning device fails to activate at 414 kPa (60 psi), the low air pressure warning device is defective. You should never need to get down to 207 kPa (30 psi).

#25. What colour is the parking brake control button?

Blue

Yellow

Orange

Red

On the dashboard, the parking brake control is a diamond-shaped, yellow, push-pull button. The trailer air supply control is an eight-sided, red, push-pull button.