Air Brakes · Practice test 4

Question 1Not answered

What could cause the parking brakes to fail to hold a vehicle even though the control has been pulled out to apply them?

1. A mechanical problem, such as worn brake components or a stuck spring, could prevent full application despite the control being set
2. Parking brakes cannot fail once the control is pulled, regardless of how the shoes or springs are adjusted
3. It only happens if the vehicle is on level ground
4. It only happens with automatic transmissions

Question 2Not answered

What should you do if you notice unusual amounts of water when performing your daily tank drain?

1. Report it, since it may indicate the air dryer or compressor is not functioning correctly
2. Ignore it, since some water in the tanks is expected every day regardless of the weather
3. Add extra oil to the system to compensate
4. Only report it if it happens more than once a month

Question 3Not answered

How can you tell the difference between the low air pressure warning and the ABS malfunction lamp on the dashboard?

1. The ABS lamp only appears when air pressure is critically low
2. They are separate, differently labeled indicators; the low air warning relates to air pressure while the ABS lamp relates to the antilock system
3. The low air warning only appears after the ABS lamp has already been lit for a while, since the two systems share a single bulb
4. There is no difference, they mean the exact same thing

Question 4Not answered

How does automatic slack adjustment technology differ from older manual slack adjusters?

1. It eliminates the need to ever inspect the brakes
2. Automatic adjusters only exist on newer trailers, never on tractors or straight trucks at all
3. It continuously compensates for lining wear so the pushrod stroke stays within limits without manual adjustment
4. It requires manual adjustment more often than older systems

Question 5Not answered

The low air pressure warning activates while you are driving. What should you do?

1. Continue to your destination at normal speed without changing anything about how you're driving
2. Slow down slightly and continue as usual
3. Stop as soon as safely possible and do not continue driving until the problem is fixed
4. Turn off the warning buzzer and keep driving

Question 6Not answered

If the low air pressure warning device itself seems to be malfunctioning, such as never activating even when you fan the brakes with the engine off, what should you conclude?

1. It's fine to drive, since a malfunctioning warning has nothing to do with whether the brakes work or hold properly
2. The warning device is not actually required equipment, so a malfunction can be ignored
3. You should disconnect the warning device entirely so it stops giving false readings
4. The vehicle has a real problem that needs to be found and fixed before the vehicle is driven, since you cannot confirm the warning would protect you

Question 7Not answered

What should a driver do if the brakes begin to feel less responsive (fading) partway down a long grade?

1. Downshift further if possible and use an escape ramp if one is available, rather than continuing to press harder on the same brakes
2. Pump the brakes rapidly and continue at the same speed
3. Shift into neutral to reduce engine strain
4. Ignore the change since brake fade usually resolves on its own without slowing down or downshifting

Question 8Not answered

Who should actually perform an adjustment on a brake that a driver finds out of adjustment during inspection?

1. A qualified mechanic, since brake adjustment work needs the right training and tools to be done safely
2. No one needs to adjust it as long as the vehicle can still move forward
3. The driver should always adjust it themselves on the roadside regardless of training, since it saves time
4. Any passenger who happens to be present, as long as they're willing to help

Question 9Not answered

What should a driver do immediately after the low air pressure warning activates while driving?

1. Continue to the destination since the warning resets itself automatically
2. Increase speed to reach a repair shop faster
3. Stop as soon as safely possible and find and fix the cause before continuing
4. Turn off the warning buzzer and keep driving

Question 10Not answered

What sign might indicate that oil has contaminated the air brake system?

1. A brighter than usual dashboard warning light color, which fades again once the engine warms up
2. Improved brake pedal feel
3. A slightly louder horn sound
4. An oily residue in the drained tank water or a burning oil smell near the compressor

Question 11Not answered

What is a common visible sign that a brake may be out of adjustment?

1. The brake chamber is a specific paint color
2. The tire pressure runs slightly below the recommended level, unrelated to the brake's own adjustment
3. The slack adjuster arm forms noticeably more than a 90-degree angle to the pushrod when the brakes are fully applied
4. The wheel has recently been washed

Question 12Not answered

What does an air dryer do in a modern air brake system?

1. It removes moisture from the compressed air before it reaches the storage tanks
2. It dries the exterior of the vehicle after washing, confusing its name with a completely unrelated exterior task
3. It only functions when the parking brake is engaged, not while driving
4. It replaces the need to ever drain tanks

Question 13Not answered

What should you do when driving down a long, steep grade with an air brake system?

1. Apply the parking brake partway down to assist the service brakes, then release it once speed drops
2. Ride the brakes continuously to keep speed as low as possible
3. Select a low gear before starting down the grade and use snub braking to control speed
4. Shift to neutral and coast to save fuel

Question 14Not answered

As part of the pre-trip air brake check, what should you do to test that the parking brake actually holds the vehicle?

1. Rely solely on the dashboard warning light with no physical test
2. Test it only after the vehicle has already been driven for several miles
3. Only check that the parking brake knob is pulled out, without applying it to see if it actually holds
4. Set the parking brake, then gently try to move the vehicle forward in a low gear to confirm it holds

Question 15Not answered

How does the parking brake valve typically work in relation to air pressure, in terms of push or pull control?

1. Pulling the control out releases the parking brakes rather than applying them, the opposite of how it actually works
2. The control has no relationship to air pressure at all
3. Pushing the control in releases the parking brakes (using air pressure to hold springs back), and pulling it out applies them
4. Pulling the control out always releases the parking brakes

Question 16Not answered

Why is it useful to repeat the slack adjuster travel check at every pre-trip inspection rather than trusting the last check?

1. Slack adjusters can drift out of proper adjustment gradually with normal use, so a check that passed last time may not still be accurate
2. Slack adjusters never change once they are set at the factory, making repeat checks unnecessary busywork every single time
3. Checking it again is only necessary after a tire change, never otherwise
4. The check is required only once a year, not at every single pre-trip inspection

Question 17Not answered

During a pre-trip inspection, why should you also check the amount of free play in the brake pedal before it engages?

1. Pedal free play only matters for driver comfort, not brake adjustment
2. Excess play can be a sign of a problem in the linkage or valves, similar to how excess pushrod travel signals a brake out of adjustment
3. Free play in the pedal is only a comfort feature with no safety relevance, since the linkage itself cannot wear out or loosen over time
4. Checking pedal play is only necessary on vehicles without air brakes

Question 18Not answered

Why should the pre-trip air brake inspection include checking the condition of the brake linings or pads, where visible?

1. Linings only need to be checked once a year, not during daily pre-trip stops before each run
2. Excessively worn or contaminated linings reduce braking effectiveness even if the air system itself works perfectly
3. Lining condition has no bearing on overall braking performance
4. It is checked only for cosmetic reasons

Question 19Not answered

Why is it important that compressed air used for brakes stay free of significant contamination, more so than air used for other vehicle systems?

1. It only matters for air used in tires, not brakes
2. Brake air quality standards are no stricter than those for the cabin air vents or the horn
3. Brake performance depends directly on how reliably that air can move through valves and chambers on demand
4. Contamination affects only accessory systems like the horn, never the brakes

Question 20Not answered

What does the tractor protection valve do if the trailer's air supply line breaks or separates?

1. It shuts off the engine to force the vehicle to stop immediately
2. It has no function related to a broken air line, only to trailer lighting
3. It opens fully so the tractor sends every bit of its remaining air to the trailer regardless of the leak
4. It closes automatically to keep the tractor's own air supply from draining away through the broken line

Question 21Not answered

What does the term 'spring brakes' refer to on a heavy vehicle?

1. An older term for the vehicle's shock absorbers
2. A soft suspension system that absorbs bumps in the road independent of braking, found mainly on older trailers
3. A set of brakes held on by powerful springs, released by air pressure, that apply automatically if air pressure is lost
4. A backup horn that activates when the main horn fails

Question 22Not answered

Why does descending a long grade increase overall stopping distance compared to flat ground at the same speed?

1. Grade only affects steering, never braking distance
2. Going downhill actually shortens stopping distance, since gravity assists the brakes and adds extra stopping force
3. Stopping distance is not affected by grade at all, only by the vehicle's speed
4. Gravity is adding to the vehicle's momentum going downhill, so the brakes have to work against both speed and the pull of the grade

Question 23Not answered

What does an air dryer do in a modern air brake system?

1. It increases the temperature of the compressed air slightly as a side effect of drying it, which is incidental and not its primary purpose
2. It removes moisture from the compressed air before it reaches the tanks, reducing the contamination that draining alone has to handle
3. It dries the windshield using leftover system air
4. It replaces the need for a governor

Question 24Not answered

Why is it important to select your descent gear before starting down a grade rather than while already on it?

1. It's required only by company scheduling policy, not for control on the grade itself, since gear choice has no real safety role
2. Gear selection has no real timing requirement
3. Shifting gears, especially downshifting, can be difficult or risky to do smoothly once already moving down a steep grade gaining speed
4. It's only a fuel efficiency consideration

Question 25Not answered

What should you check about the parking brake control before starting a trip?

1. That it moves freely between set and released positions and that the corresponding dashboard indicator responds correctly
2. Nothing, since the parking brake control is checked only at the annual inspection, not before every trip
3. That it is permanently locked in the released position
4. Only that it is a specific color

Question 26Not answered

Where should you park a vehicle if you must leave it with the parking brakes released, such as in very cold weather where they might freeze?

1. Somewhere the vehicle can be safely secured another way, such as with wheel chocks, since brakes should not be routinely left released
2. Anywhere convenient, since released brakes present no risk
3. Only on a downhill grade, to make the next departure easier
4. It does not matter, since the wheels stay locked regardless of temperature or how long the vehicle sits

Question 27Not answered

What braking technique is recommended for a long downgrade to avoid overheating the brakes?

1. Hold steady, firm pressure on the brakes for the whole way down without ever releasing them
2. Pump the brakes as rapidly as possible
3. Avoid using the brakes at all on any downgrade
4. Apply the brakes firmly enough to slow a bit below your target speed, then release, repeating in a controlled cycle

Question 28Not answered

What safety habit should a driver follow every time before getting out of the cab, even for a brief stop?

1. Rely on the vehicle's weight alone to prevent rolling
2. Leave the vehicle in gear as the only safeguard, without setting the parking brake
3. Only set the parking brake if leaving the vehicle for more than an hour
4. Confirm the parking brake is set before leaving the vehicle unattended

Question 29Not answered

If a vehicle equipped with automatic slack adjusters shows signs of excessive brake stroke, what does this suggest?

1. It only means the tires are due for replacement
2. It is a normal reading and requires no action
3. Automatic adjusters can never malfunction, so the reading must be a sensor error
4. The automatic adjuster itself may be malfunctioning and needs inspection or repair

Question 30Not answered

Why is contaminated air a greater concern in a system without a properly functioning air dryer?

1. Contaminated air is never a concern as long as the tanks get drained occasionally during routine maintenance
2. A malfunctioning dryer only affects the trailer, never the tractor
3. Air dryers only affect fuel economy, not contamination
4. Without effective drying, more moisture and oil reach the valves and brake components where they can cause problems