Air Brakes · Practice test 5

Question 1Not answered

What is a quick release valve used for in an air brake system?

1. It lets a driver dump the entire air tank at once, something otherwise impossible to do without a service technician present
2. It slows down how quickly the brakes apply once the pedal is pressed
3. It lets air out of the brake chambers quickly when the brakes are released, so the brakes disengage fast instead of dragging
4. It has nothing to do with brake timing, only with the horn circuit

Question 2Not answered

How can contaminated air affect the timing of brake application, beyond just risking valve damage?

1. Timing of brake application is fixed mechanically and never affected by air supply issues
2. It only affects the color of the exhaust, not braking response
3. Buildup inside lines and valves can slow how quickly air reaches the brake chambers, adding lag to when the brakes actually engage
4. Contaminated air always makes the brakes apply faster than normal, which is actually helpful during panic stops on wet roads

Question 3Not answered

What does the 'governor' do in an air brake system?

1. It only operates the parking brake valve
2. It controls when the air compressor pumps air into the tanks and when it stops, based on system pressure
3. It limits the maximum speed of the vehicle rather than the compressor's pressure cycle or cutout point
4. It measures brake lining thickness

Question 4Not answered

Why is choosing your gear before starting down a grade, rather than midway, especially important for a fully loaded truck?

1. Loaded trucks handle grades identically to empty ones, so gear timing does not matter at all
2. A loaded vehicle gains momentum quickly, and shifting once already descending can be difficult or unsafe
3. It only matters for trucks without a manual transmission
4. Gear timing is irrelevant as long as the brakes are in good condition

Question 5Not answered

What is the risk of setting only some of a vehicle's parking brakes, such as just one axle, rather than the full set?

1. It is standard practice recommended by manufacturers
2. It has no bearing on whether the vehicle stays in place
3. The vehicle may not be adequately held in place, especially under load or on an incline
4. Setting brakes on just one axle always provides the same holding power as the full set

Question 6Not answered

Why should air tanks be drained regularly, especially in cold or humid climates?

1. Draining tanks only matters in vehicles built before the 1990s, since newer systems are fully sealed
2. To remove accumulated water and oil before they can cause a freeze-up or reduce system performance
3. Draining tanks is done only to reduce vehicle weight
4. It is only necessary once a year regardless of climate

Question 7Not answered

If some brakes on a vehicle are properly adjusted and others are not, what problem can that mismatch create beyond just reduced total stopping power?

1. Mismatched adjustment only affects fuel economy, not how the vehicle handles while braking
2. The brakes automatically balance themselves out during hard stops regardless of adjustment
3. The properly adjusted brakes end up doing more of the work, which can cause uneven braking and even pull the vehicle to one side
4. A mismatch in adjustment across brakes has no effect as long as most of the brakes are still working properly

Question 8Not answered

Before setting out on a trip that includes a long, steep downgrade, what should you do regarding your planned speed?

1. Plan to maintain highway speed the entire way down to save time
2. Check for and follow any posted safe speed for the grade, planning your gear selection around it in advance
3. Ignore posted grade speeds since they are only suggestions for cars, a reading of the signs that doesn't match how they're actually posted for all vehicle types
4. Plan to use whatever speed feels comfortable once already on the grade

Question 9Not answered

What effect can a brake that is adjusted too tight have on the vehicle?

1. It can drag continuously, causing excessive heat and premature wear even when the brake pedal is not pressed
2. It only affects fuel economy, never brake wear
3. A too-tight brake behaves exactly like a correctly adjusted one under normal driving conditions
4. It improves stopping power with no downside

Question 10Not answered

What happens to the spring brakes if a vehicle loses enough air pressure while parked, even if the driver never touched the parking brake control?

1. The spring brakes apply automatically once pressure drops low enough, holding the vehicle even without driver action
2. Nothing happens, since spring brakes only ever respond to the driver's own parking brake control lever
3. The engine restarts automatically to rebuild pressure before anything else happens
4. The vehicle's wheels are released completely, making it easier to roll away

Question 11Not answered

You notice a brake seems out of adjustment during a pre-trip check. Why shouldn't you try to adjust it yourself unless qualified?

1. Improper adjustment can leave the brake working incorrectly in a way that isn't obvious, so it should be handled by someone trained to do it correctly
2. Adjusting brakes yourself is always faster and just as safe as a qualified technician's work, since the process is the same either way
3. Only a locksmith is legally allowed to adjust brakes
4. It's only a paperwork issue, not a mechanical one

Question 12Not answered

What is the purpose of the foot valve, also called the treadle valve or service brake pedal?

1. It is used exclusively to sound the vehicle's horn, since the treadle valve has no connection to the service brakes
2. It regulates engine RPM during braking
3. It controls how much air pressure is sent to the brake chambers when the driver presses the brake pedal
4. It only controls the parking brake

Question 13Not answered

Why can a brake that runs unusually hot after a trip be a sign of improper adjustment?

1. A hot brake means it is adjusted more tightly than necessary, which is actually the safest setting, when a brake running that hot is usually dragging and wasting energy rather than braking any better
2. Heat on the brakes after driving is completely normal and never indicates an adjustment problem
3. A dragging or improperly adjusted brake can create constant friction that builds excess heat even when the driver isn't actively braking hard
4. Only the engine can run hot from a mechanical problem; brake heat comes only from the sun

Question 14Not answered

While performing the pre-trip air brake check on a combination vehicle, you also check that the trailer's air lines connect properly at the glad hands. What are you making sure of?

1. That the connections are secure and sealed, without leaks, so both the service and supply lines charge the trailer correctly
2. That the glad hands match the color of the tractor
3. That the glad hands are painted the correct color
4. Only that the connections look tight, without checking for actual leaks, which a hose that is pulling air can still pass by eye

Question 15Not answered

What is an advantage of automatic slack adjusters over manual ones?

1. They eliminate the need for any brake inspections at all, since the system is fully self-correcting for every kind of mechanical brake fault
2. They continually compensate for normal brake lining wear, reducing the chance of the brake falling out of adjustment between inspections
3. They only work on trailers, not tractors
4. They apply more braking force than manual adjusters

Question 16Not answered

What is the purpose of the two air pressure gauges on the dashboard of a vehicle with a dual air brake system?

1. They both show the same reading and exist only because of an older design standard
2. One shows fuel pressure and the other shows oil pressure, unrelated to the brakes themselves or the air tanks
3. One gauge is just a spare in case the other one breaks, and both always read the same value
4. One shows pressure for the primary system and one for the secondary system, so a driver can tell if either has failed

Question 17Not answered

What should you do if, during the pre-trip check, you find a cracked or damaged air hose anywhere in the brake system?

1. Have it repaired or replaced before driving, since a damaged hose can leak or fail under pressure
2. Ignore minor cracks that are not currently leaking air, since they rarely get any worse over time
3. Only address it if the hose is completely severed
4. Wrap it with tape and continue the trip as planned

Question 18Not answered

Why should you never use the trailer's spring parking brakes as a substitute for the service brakes while the vehicle is moving?

1. It only wastes air pressure and has no effect on trailer handling
2. Applying them at speed can cause the trailer wheels to lock and the trailer to skid, since they are not designed for graduated braking
3. It is illegal but not actually dangerous
4. It has no real risk, since spring brakes are just as smooth as service brakes at speed and never lock the wheels

Question 19Not answered

You check the automatic drain valve on an air tank and find it caked with dirt and not draining. What should this tell you?

1. The tank is simply too full of air to drain
2. The dirt indicates a fuel leak rather than an air system issue, since both fluids can leave a similar-looking residue around a fitting
3. A clogged drain valve is a cosmetic issue with no effect on moisture buildup
4. The valve may not be removing moisture and oil as intended, and the tank should be checked and drained manually

Question 20Not answered

You notice your vehicle takes noticeably longer to stop than usual, though the brakes still work. What is a likely cause?

1. One or more brakes may be out of adjustment and not applying full force
2. The tire pressure is too high, unrelated to how the brakes themselves respond
3. The mirrors are misaligned
4. The fuel filter is clogged

Question 21Not answered

In freezing weather, why might a driver notice the low air pressure warning activate suddenly even though the tanks seemed full moments earlier?

1. Cold weather always increases air pressure readings rather than lowering them overnight
2. It indicates the parking brake was engaged intentionally
3. Ice may have formed and blocked a line or valve, disrupting normal air pressure delivery
4. The warning system only functions in warm weather

Question 22Not answered

Why should you avoid overfilling the air system with excessive oil-based lubricants during maintenance?

1. Excess oil can migrate into the air lines and contaminate valves and chambers
2. Extra oil-based lubricant only helps seals last longer, nothing else worth noting
3. It only matters for the trailer's electrical system
4. Oil-based lubricants have no interaction with the air brake system

Question 23Not answered

How is the low air pressure warning usually tested as part of the pre-trip air brake inspection?

1. By fanning or applying the brakes with the engine off until pressure drops to the warning point and confirming the alert activates
2. By listening to the engine at idle for unusual noise
3. By inspecting the tire tread depth
4. By confirming the warning bulb glows a certain shade with the ignition switched off and the engine cold

Question 24Not answered

At what general air pressure level does federal regulation require the low air pressure warning to activate?

1. At 100 psi, the same as full system pressure
2. At or before 60 psi, or as specified by the manufacturer if lower
3. Exactly at 0 psi, once all air has been lost, far too late for the warning to give any useful notice
4. Only after the parking brake has already been manually released

Question 25Not answered

An air dryer's desiccant cartridge is due for replacement but hasn't been changed. What is the risk?

1. The dryer becomes less effective at removing moisture, so more water can reach the tanks and brake components
2. The compressor will stop building air pressure completely
3. The horn will stop working until it's replaced
4. It has no effect, since the cartridge only filters dust from the cab vents, not the brake air supply itself

Question 26Not answered

How long should you generally wait after startup for air pressure to build from a low level to a safe operating level, as part of checking compressor performance?

1. About 45 seconds or less to reach a full operating pressure, per typical manufacturer guidance, or as specified for your vehicle
2. Build-up time is not something drivers check during a pre-trip
3. Air pressure should build to full operating level within seconds no matter the outside temperature or altitude
4. Only the parking brake pressure needs to build; service brake pressure is irrelevant

Question 27Not answered

Why should the pre-trip air brake check include listening for air leaks around fittings and valves with the engine running?

1. An audible hiss can reveal a leak that a visual inspection alone might miss
2. Listening for leaks is only useful once the vehicle is already moving down the road
3. It is done only to check the horn's air supply
4. Air leaks are always silent and cannot be detected by ear

Question 28Not answered

On a vehicle equipped with spring parking brakes, what happens if you try to release the parking brake without enough air pressure built up?

1. The parking brake releases normally regardless of air pressure
2. The parking brake will not release, or will not stay released, until enough air pressure is available to hold the springs back
3. The vehicle will roll forward slightly, then the brake resets on its own
4. The service brakes take over automatically and work at full strength instead, since they don't depend on air pressure like the parking brake does

Question 29Not answered

During a pre-trip air brake check, you should confirm air pressure builds from a low level to a safe operating range within about how much time, according to general guidance?

1. It doesn't matter how long it takes as long as it eventually builds up
2. A reasonably short, specified time while the engine runs at a fast idle, not an unlimited amount of time
3. Only the time to reach maximum pressure matters, not the time needed to reach a safe range for driving
4. Build-up time is not something a pre-trip inspection checks at all

Question 30Not answered

What maintenance practice helps reduce the amount of oil that gets into the air brake system over time?

1. Keeping the air compressor properly serviced so its internal seals do not let oil pass into the airflow
2. Adding extra engine oil to the air tanks
3. Disconnecting the air dryer to increase airflow
4. Draining tanks less often so more oil has time to settle out before the next scheduled service