New Day: Mon Aug 28 2023 12:30:13 GMT-0500 (Central Daylight Time)
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Grand set:
The spring brakes used on tractors and straight trucks will bring your truck to a stop when the air pressure drops below:
20 psi.
Excessive heat caused by using your brakes too often can cause the:
brakes to fade or fail
If air pressure does NOT build up to normal within the correct amount of time, then:
your air pressure may drop to low driving, requiring an emergency stop.
If your truck has dual air system and one of the systems is low on pressure:
either the front or rear brakes will not be gully operational.
In air brakes vehicles, the parking brakes should be used:
any time the vehicle is parked.
The braking power of the spring brakes:
depends on the service brakes being in adjustment.
The driver must be able to see a warning before air pressure in the service air tanks falls below:
60 psi.
The use of air brakes on a long and/or steep downgrade under normal conditions is only supplement to:
the braking effect of the engine.
The air compressor governor controls:
when air is pumped into the air tanks.
The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like:
spring pressure.
The brake pedal in an air brake system:
Controls the air pressure applied to put on the brakes.
If you must make an emergency stop, brake so you :
Can steer and your vehicle stays in a straight line.
A supply pressure gauge tells you how much air is in the:
air tanks.
Under normal conditions, in order to engage the parking brakes the driver must first:
let the air out of the air brake system.
For air brake systems in good condition, the air compressor should start pumping at about:
100 psi
When is it OK to leave your truck without applying the parking brake or chocking the wheels?
never.
Under ideal conditions, a truck with air brake going 55 miles per hour would require a stopping distance of:
more than 300 feet.
Air braking takes more time than hydraulic braking because:
air takes more time to flow through the line than fydrauli fluids.
If you are driving down a steep downgrade and you have reached your “safe” speed f 40 mph, you would apply the service rakes until your speed drops to:
35 mph.
A slack adjuster probably needs to be adjusted if it moves more than about:
1 inch when you pull hard on it
During normal driving spring brakes are usually held back by:
air pressure.
Emergency stab braking is when you:
brake as hard as you can, release the bakes hen the wheels lock, put on the brakes again when the wheels start rollling
How should you check that the spring brakes come on when air pressure in the system drops below a certain level?
park on level ground, chock the wheels, release the parking brake when you have enough air pressure shut the engine off and repeatedly press and release the brake pedal.
Excessive use of the service brakes results in over-heating, which can lead to:
Expansion of the brake drums.
The most important thing to do when a low air pressure warning come on is:
stop and safely park as soon as possible.
An air brake system is fully charged at:
125 psi.
To check the free play of manual slack adjuster on S-Cam brakes, you should park on:
level ground, chock the wheels, and turn of the parking brakes.
Your truck or bus has a dual air brake system. If a low air pressure warning comes only one system, what should you do?
stop right away and safely park. Continue only after the system is fixed.
Your vehicle has a dual air brake system. If a low air pressure warning comes on for the secondary system, you should?
bring the vehicle to a safe stop and continue only when the system is fixed.
The S-Cam:
forces the brake shoes against the inside of the brake drum.
The brake system that applies and releases the brakes when the driver uses the brake pedal is the:
service brake system.
The application pressure gauge shows how much air pressure you:
are applying to the brakes
Modern air brake systems combine three different systems. They are the service, parking and the:
emergency brakes.
The air compressor should stop pumping at about:
125 psi.
The safety valve is set to automatically reduce pressure at:
150 psi.
If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:
release the spring emergency/parking brakes to move a short distance.
If you must make an emergency stop, brake so you:
can steer and your vehicle stays in a straight line.
With air brake vehicle, the parking brakes should be used:
whenever leave the vehicle unattended.
Emergency controlled braking is when you:
brake as hard as you can, release the brakes when the wheels lock and put the brakes back on again when the wheels start rolling.
The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like:
a. Fluid pressure
b. Spring pressure
c. Air pressure
d. Any of the above
b. Spring pressure
A straight truck or bus air brake system should not leak at a rate of more than __ psi per minute with the engine off and the brake released.
a. 1
b. 2
c. 3
d. 4
c. 3
Your vehicle has dual air brake system. If low air pressure warning comes on for the secondary system or for one system, you should:
a. Bring the vehicle to a safe stop and continue only when the system is fixed.
b. Reduce your speed, and test the remaining system while under-way.
c. Reduce your speed, and drive to the nearest garage for repairs.
d. Continue at normal speed if only the secondary system fails.
a. Bring the vehicle to a safe stop and continue only when the system is fixed.
If your vehicle has an alcohol evaporator, it is there to:
a. Rid the wet tank of alcohol that condenses and sits at the bottom.
b. Eliminate the need for daily tank draining.
c. Boost tank pressure the same way that superchargers boost engines.
d. Reduce the risk of ice in the air brake valves in cold weather.
d. Reduce the risk of ice in the air brake valves in cold weather.
Air braking takes more time than hydraulic because air:
a. Brakes use different brake drums.
b. Takes more time to flow through the lines than hydraulic fluid.
c. Brakes require heavier return springs.
d. Is always leaking through airline fittings.
b. Takes more time to flow through the lines than hydraulic fluid.
The brake pedal in an air brake system:
a. Controls the speed of the air compressor.
b. Always needs to be held down halfway during normal driving.
c. Controls the air pressure applied to put on the brakes.
d. Is connected to slack adjusters by a series of rods and linkages.
c. Controls the air pressure applied to put on the brakes.
With air brake vehicles, the parking brakes should be used:
a. Whenever you leave the vehicle unattended.
b. To hold your speed when going downhill.
c. As little as possible.
d. Only during pre and post-trip inspections.
a. Whenever you leave the vehicle unattended.
For emergency stab braking, you should:
a. Pump the brake pedal rapidly and lightly.
b. Press on the brake pedal as hard as you can, release the brakes when the wheels lock, and when the wheels start rolling put on the brakes fully again.
c. Brake hard until the wheels lock, then get off the brakes for as much time as the wheels were locked.
d. Press hard on the brake pedal and apply full hand valve until you stop.
b. Press on the brake pedal as hard as you can, release the brakes when the wheels lock, and when the wheels start rolling put on the brakes fully again.
If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:
a. Release the spring emergency/ parking brakes to move a short distance.
b. Apply more brake pressure if the main tank is getting low.
c. Stay parked twice as long with your service air pressure.
d. Balance the service brake system whenever you are parked.
a. Release the spring emergency/ parking brakes to move a short distance.
Modern air brakes systems combine three different systems. They are the service, parking, and the _ brakes.
a. Emergency
b. Foot
c. S-cam
d. Drum
a. Emergency
To check the free play of the manual slack adjusters on the S-cam brakes, you should park on:
a. Level ground with the parking brake on, then apply the service brake.
b. Level ground, chock the wheels, and turn off the parking brakes.
c. Level ground and drain off air pressure before adjusting.
d. A slight grade, release the parking brake, apply the service brake and check for vehicle movement.
b. Level ground, chock the wheels, and turn off the parking brakes.
Of the choices below, the first thing to do when a low air pressure warning comes on is:
a. Stop and safely park as soon as possible.
b. Shift to next higher gear.
c. Adjust the brake pedal for more travel.
d. Open the air supply control valve.
a. Stop and safely park as soon as possible.
The air compressor governor controls:
a. The speed of the air compressor.
b. When the brake chambers release pressure.
c. Air pressure is applied to the brakes.
d. When air is pumped into the air tanks.
d. When air is pumped into the air tanks.
The braking power of the spring brakes:
a. Is not affected by the condition of the service brakes.
b. Can only be tested by highly trained brake service people.
c. Depends on the service brakes being in adjustment.
d. Increases when the service brakes are hot.
c. Depends on the service brakes being in adjustment.
To test air service brakes, you should brake firmly when moving slowly forward. The brakes are “OK” if you notice:
a. A delayed stopping action.
b. An unusual feel.
c. The vehicle “pulls” to one side.
d. None of the above.
d. None of the above.
On long downhill grades, experts recommend using a low gear and light pedal pressure instead of on-again, off-again braking. Why?
a. Air usage is less with light steady pressure.
b. Brake linings do not heat up as much with light pressure.
c. You can keep vehicle speed constant in a low gear with light, steady pressure.
d. All the above.
b. Brake linings do not heat up as much with light pressure.
All air brake equipped vehicles have:
a. At least one brake heater.
b. A hydraulic system, in case the air system fails.
c. A supply pressure gauge.
d. An air usage gauge.
c. A supply pressure gauge.
If you must make an emergency stop, brake so you:
a. Can steer hard while braking hard.
b. Use the full power of the brakes and lock them.
c. Can steer and your vehicle stays in a straight line.
d. Use the hand brake first.
c. Can steer and your vehicle stays in a straight line.
The application pressure gauge shows how much air pressure you:
a. Have used this trip.
b. Have in the air tanks.
c. Are applying to the brakes.
d. None of the above.
c. Are applying to the brakes.
If you do not have automatic tank drains, how often should you drain the oil and water from the bottom of compressed air storage tanks?
a. After every four hours of service.
b. At the end of each day of driving.
c. Once a week.
d. Every other week.
b. At the end of each day of driving.
You should know that your brakes are “fading” when:
a. You have to push harder on the brake pedal to control your speed on a downgrade.
b. The brake pedal feels spongy when pressure is applied.
c. Pressure on the brake pedal is released and speed increases.
d. Less pressure is needed on the brake pedal for each stop.
a. You have to push harder on the brake pedal to control your speed on a downgrade.
If your vehicle has an alcohol evaporator, every day during cold weather you should:
a. Change the alcohol from a new bottle.
b. Clean the air filter with alcohol.
c. Check the oil for an alcohol content.
d. Check and fill the alcohol level.
d. Check and fill the alcohol level.
The brake pedal in an air brake system:
a. Controls the speed of the air compressor.
b. Is seldom used, compared to hydraulic systems.
c. Controls the air pressure applied to put on the brakes.
d. Is connected to slack adjusters by a series of rods and linkages.
c. Controls the air pressure applied to put on the brakes.
The driver must be able to see a low pressure warning which comes on before pressure in the service air tanks falls below __ psi.
a. 20
b. 40
c. 60
d. 80
c. 60
Why drain water from compresses air tanks?
a. The low boiling point of water reduces braking power.
b. Water can freeze in cold weather and cause brake failure.
c. Water cools the compressor too much.
d. To keep from fouling the air compressor oil.
b. Water can freeze in cold weather and cause brake failure.
During normal driving, spring brakes are usually held back by:
a. Bolts
b. Air Pressure
c. Spring pressure
d. Centrifugal force
b. Air Pressure
Total stopping distance for air brakes is longer than for hydraulic brakes due to _ distance.
a. Perception
b. Reaction
c. Brake lag
d. Effective braking
c. Brake lag
The most common type of foundation brake found on heavy vehicles is the:
a. Disc.
b. Wedge drum.
c. S-cam.
d. None of the above.
c. S-cam.
The air loss rate for a straight truck or bus with the engine off and the brakes on should be more than:
a. 1 psi in 30 seconds.
b. 1 psi in 1 minute.
c. 2 psi in 45 seconds.
d. 3 psi in 1 minute.
d. 3 psi in 1 minute.
The supply pressure gauge shows how much pressure:
a. You have used in this trip.
b. Is in the air tanks.
c. Is going to the brake chambers.
d. The air can take.
b. Is in the air tanks.
The brake system that applies and releases the brakes when the driver uses the pedal is the __ brake system.
a. Emergency.
b. Service.
c. Parking.
d. None of the above.
b. Service.
The important thing to do when a low air pressure warning comes on is to:
a. Up-shift
b. Down-shift
c. Adjust the brake pedal
d. Stop and safely park as soon as possible.
d. Stop and safely park as soon as possible.
Third set:
The air brake lag distance at 55 MPH on a dry pavement adds about _ feet to your stopping distance. 32 Repeatedly pressing and releasing (fanning) the brake pedal may result in: A loss of brake air pressure. The air brake compressor should stop pumping at about PSI.
125
All air brake equipped vehicles have:
An air supply pressure gauge.
Emergency controlled braking is when you:
Apply the brakes as had as you can without locking the wheels.
The braking power of the spring brakes:
Depends on the service brakes being in adjustment.
During normal driving spring brakes are usually held back by:
Air pressure.
The safety valve is usually set to automatically reduce pressure at PSI.
150
If your truck’s air compressor has its own oil supply, when should you check the oil level?
Before driving.
Emergency stab braking is when you:
Brake as hard as you can, release the brakes when the wheels lock, and put on the brakes again when the wheels start rolling.
If your vehicle has an alcohol evaporator, it is there to:
Reduce the risk of ice in air brake lines in cold weather.
The application pressure gauge shows how much air pressure you:
Are applying to the brakes.
The most important thing to do when a low air pressure warning comes on is:
Stop and safely park as soon as possible.
Your vehicle has a dual air brake system. If a low air pressure warning comes on for the secondary system, you should:
Bring the vehicle to a safe stop and continue only when the system is fixed.
If your truck has a properly functioning dual air brake system and minimum size air tanks, the air pressure should build from 85 to 100 PSI within seconds.
45
How should you check that your service brakes are working properly?
Park on level ground, wait for normal air pressure, release the parking brake, move the truck forward slowly (about 5 MPH) and apply the brakes firmly using the brake pedal.
If you must make an emergency stop, brake so that you:
Can steer and your vehicle stays in a straight line.
When the brakes are applied, the brake shoes (or linings) are pressed against the:
Brake drum or disc.
Under ideal conditions, a truck with air brakes going 55 MPH would require a stopping distance of:
More than 300 feet.
The use of are brakes on a long and/or steep downgrade under normal conditions is only a supplement to:
The braking effect of the engine.
To check the free play of manual slack adjusters on S-cam brakes, you should park on:
Level ground, chock the wheels, and turn off the parking brakes.
A straight truck or bus air brake system should not leak at a rate of more than PSI per minute with the engine off and the brakes released.
2
The air compressor governor controls:
When air is pumped into the air tanks.
The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like:
Spring pressure.
The brake pedal in an air brake system:
Controls the air pressure applied to put on the brakes.
Some air brake systems have an alcohol evaporator. What may happen if you don’t keep the unit filled with alcohol?
Ice may form in the air storage tanks and cause the brakes to fail.
The brake system that applies and releases the brakes when the driver uses the brake pedal is the system.
Service.
Before driving a truck or bus with a dual air brake system, the pressure in each system should be at least PSI.
100
Your truck or bus has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do?
Stop right away and safely park. Continue only after the system is fixed.
How should you check that your service brakes are working properly?
Wait for normal pressure, release the parking brake, move the truck forward slowly, and apply the brakes firmly using the brake pedal.
Emergency stab braking is when you:
Brake as hard as you can, release the brakes when the wheels lock, and put the brake back on when the wheels start rolling.
If air pressure does NOT build up to normal within the correct amount of time, then:
Your air pressure may drop too low during driving, requiring an emergency stop.
Which of these is NOT a proper time to apply the parking brakes?
If the brakes are very hot. (E.G. just after coming down a steep grade.)
Excessive use of the service brakes results in overheating, which can lead to:
Expansion of the brake drums.
The proper method of braking when going down long and/or steep grades, after selecting the proper gear, is to brake until your speed is about MPH below your “safe” speed, and then release your brakes.
5
Under normal conditions, in order to engage the parking brakes the driver must first:
Let the air out of the brake system.
Total stopping distance for air brakes is longer than that for hydraulic brakes due to distance
Brake lag.
If you must make an emergency stop, you should brake so you:
Can steer and so your vehicle can stay in a straight line.
If your truck has dual parking control valves, you can use pressure from a separate tank to:
Release the spring emergency/parking brakes to move a short distance.
The driver must be able to see a warning before air pressure in the service air tanks falls below PSI.
60
The stop light switch:
Turns on the brake lights to warn others behind you.
For air brake systems in good condition, the air compressor should start pumping at about PSI.
100
The air loss rate for a straight truck or bus with the engine off and the brakes on should not be more than:
3 PSI in one minute.
The braking power of the spring brakes:
Depends on the service brakes being in adjustment.
How should you check that the spring brakes come on when air pressure in the system drops below a certain level?
Chock the wheels, apply the parking brake, shut the engine off, pump the brake pedal to reduce air tank pressure.
If you are driving down a steep downgrade and you have reached your “safe” speed of 40 MPH, you would apply the service brakes until your speed drops to MPH.
35
The air brake lag distance at 55 MPH on a dry pavement adds about feet to the stopping distance.
32
Repeatedly pressing and releasing (fanning) the brake pedal may result in:
The loss of brake air pressure.
Emergency controlled braking is when you:
Apply the brakes as hard as you can without locking the wheels.
If your truck’s air compressor has its own oil supply, when should you first check the oil level?
Before driving.
You should know that your brakes are fading when:
You have to push harder on the brake pedal to control your speed on a downgrade.
If the spring brakes are on, when should you push the brake pedal?
NEVER!
The driver must be able to see a low air pressure warning which comes on before pressure in the service air tanks falls below PSI.
60
If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:
Release the spring emergency/parking brakes to move a short distance.
The brake pedal in an air brake system:
Controls the air pressure applied to put on the brakes.
Parking or emergency brakes of trucks or buses can be legally held on by __ pressure,
Air
The most common type of foundation brake found on heavy vehicles is the:
S-cam drum.
If your truck has a dual air system and one of the systems is low on pressure:
Either the front or rear brakes will not be fully operational.
In air brake vehicles, the parking brake should be used:
Any time the vehicle is parked.
The air compressor governor controls:
When air is pumped into the air tanks.
Sharp School set:
Second set air brakes – sharp school
Page 1 –
AIR BRAKES PRACTICE TEST- A
1. The parking or emergency brake on a heavy vehicle can only be held into position by something that cannot leak away. An example would be?
b. Spring pressure
2. A straight truck or bus air brake system would not leak at a rate of more than how many PSI per minute with the engine off and the brakes released?
a. 1 PSI per minute
b. 2 PSI per minute
c. 3 PSI per minute
d. 4 PSI per minute
3. Your vehicle has a dual air brake system, if a low air pressure warning comes on for the secondary system what should you do?
a. Bring the vehicle to a safe stop and continue only when the system is fixed
4. If your vehicle has an alcohol evaporator, why is it there?
d. To reduce the risk of ice in air brake valves in cold weather
5. Air braking takes more time than hydraulic braking because
b. Air takes more time to flow through than hydraulic fluid
6. The brake pedal in an air brake system ______________________.
c. Controls the air pressure applied to put on the brakes
Page 2 –
7. If your truck or bus has dual parking control valves you can use pressure from a separate tank for what purpose?
c. To release the spring emergency and parking brakes to move a short distance.
8. Air brake systems combine three different systems. They are the service brake system, the parking brake system, and what other?
a. The emergency brake system
9. To check the free play of manual slack adjusters of S-CAM brakes you should park on what kind of grade?
b. Park on level ground, chock the wheels and release the parking brakes
10. Which of these is the most important thing to do when a low air pressure warning comes on?
a. Stop and safely park as soon as possible
11. What does the air compressor governor do?
d. It controls when air is pumped into the air tanks
12. The braking power of the spring brakes ___________________.
c. Depends on the service brakes being in adjustment
13. All air brake equipped vehicles have _____________________.
c. A supply pressure gauge
Page 3 –
14. If you must make an emergency stop how should you brake?
c. You brake so you can steer and your vehicle stays in a straight line
15. What does the application pressure gauge show?
c. It shows how much pressure you are applying to the brakes
16. If you do not have automatic tank drains, how often should you drain the oil and water from the air storage air tanks?
b. At the end of each day of driving
17. You know that your brakes are fading when:
a. You have to push harder on the brake pedal to control your speed on a down grade
18. If your vehicle has an alcohol evaporator, every day during cold weather what should you do?
d. Check and fill the alcohol level
19. Why drain water from compressed air tanks?
b. Water can freeze in cold weather and cause brake failure
20. To test service brakes, you should brake firmly while moving slowly forward. The brakes are O.K. if you notice:
a. The vehicle pulls to one side
b. An unusual feel
c. A delayed stopping action
d. None of the above
Page 4 –
4
21. What is the correct braking technique for driving on long downhill grades?
a. Reduce your speed to 5 MPH below your safe speed
b. Release the brakes
c. When your speed has increased to your safe speed, repeat a and b
d. All of the above
22. The driver must be able to see or hear a warning before air pressure in the storage tanks falls below what pressure?
C. 60 PSI
23. During normal driving, spring brakes are usually held back by ______.
a. Bolts
b. Air Pressure
c. Spring Pressure
d. Centrifugal force
24. In air brake vehicles the parking brakes should be used how?
b. Anytime the vehicle is parked
25. Emergency stab braking is when you ____________.
d. Brake as hard as you can, release the brakes when the wheels lock; and when the wheels start rolling press the brakes fully
1 – (b) 6 – (c) 11 – (d) 16 – (b) 21 – (d) ADD FROM TEST B #3,
2 – (b) 7 – (c) 12 – (c) 17 – (a) 22 – (A)
3 – (a) 8 – (a) 13 – (c) 18 – (d) 23 – (b)
4 – (d) 9 – (b) 14 – (c) 19 – (b) 24 – (b)
5 – (b) 10 – (a) 15 – (c) 20 – (d) 25 – (d)
Page 5 –
5
AIR BRAKES PRACTICE TEST- B
1. The air loss rate for a straight truck or bus, with the engine off and the brakes on, should not be more than what?
a. 1 PSI in 30 seconds
b. 1 PSI in 1 minute
c. 2 PSI in 45 seconds
d. 3 PSI in 1 minute
2. Your brakes are fading when _________.
a. You have to push harder on the brake pedal to control your speed on a downgrade.
b. The brake pedal feels spongy when you apply pressure.
c. You release pressure on the brake pedal and speed increases.
d. Less pressure is needed on the brake pedal for each stop.
3. What does the supply pressure gauge show?
a. It shows how much pressure you have used in this trip.
b. It shows how much pressure is in the air tanks.
c. It shows how much pressure is going to the brake chambers.
d. It shows how much pressure the air can take.
4. The brake system that supplies and releases the brakes when the driver uses the brake pedal is called what brake system?
a. The emergency brake system
b. The service brake system
c. The parking brake system
d. None of the above
5. If your vehicle has an alcohol evaporator, every day during cold weather what should you do?
a. Check and fill the alcohol level
b. Change the alcohol from a new bottle
c. Clean the air filter with alcohol
d. Check the oil for alcohol content
6. Why should you drain water from compressed air tanks?
a. The boiling point reduces braking power.
b. Water can freezes in cold weather causing brake failure.
c. Water-cools the compressor too much.
d. You should drain water to make room for the oil that should be in the compressed air tank.
7. To test air service brakes you should brake firmly when moving slowly forward. What tells you that the brakes are O.K.?
a. A delayed stopping action.
b. An unusual feel.
c. The vehicle pulls to the right.
d. None of the above.
Page 6 –
8. On long downhill grades, experts recommend using a low gear and light, steady pedal pressure instead of on-again, off-again
braking. Why is that?
a. Because air usage is less when you have light steady pressure.
b. Because brake linings do not heat up as much with light steady pressure.
c. Because you can keep vehicle speed constant in a low gear with light, steady pressure.
d. All the above.
9. Your truck or bus has a dual air brake system, if a low air pressure warning comes on for only one system, what should you do?
a. Reduce your speed and drive to the nearest garage for repair.
b. Reduce your speed and test the remaining system while underway.
c. Continue at normal speed. No action is needed if only one system fails.
d. Stop right away and safely park, continue only after the system is fixed.
10. During normal driving, spring brakes are usually held back by what?
a. Air pressure
b. Spring pressure
c. Centrifugal force
d. Bolts or clamps
11. Total stopping distance for air brakes is longer than that for hydraulic brakes, due to what distance?
a. Perception distance
b. Reaction distance
c. Brake lag distance
d. Effective braking distance
12. The most common type of foundation brake found on heavy vehicles is what?
a. The disc brake
b. The wedged drum brake
c. The S-CAM system
d. None of the above
13. With air brake vehicles the parking brakes should be used when?
a. Whenever you leave the vehicle unattended.
b. To hold the speed when going downhill.
c. As little as possible.
d. Only during pre-trip and post-trip inspections.
14. What is emergency stab braking?
a. Pump the pedal lightly and rapidly
b. Press on the brake pedal as hard as you can, then release the brakes when the wheels lock; and when the wheels start rolling put the brakes on fully again.
c. Brake hard until the wheels lock, then get off the brakes for as much time as the wheels were locked.
d. Press hard on the brake pedal and apply full hand valve until you come to a stop.
Page 7 –
7
15. Parking or emergency brakes of trucks and buses are held on by what kind of pressure?
a. Spring pressure
b. Fluid pressure
c. Air pressure
d. Atmospheric pressure
16. The driver must be able to see a low air pressure warning, which comes on before pressure in the service air tanks falls below how
many PSI?
a. 20 PSI
b. 40 PSI
c. 60 PSI
d. 80 PSI
17. If your vehicle has an alcohol evaporator, why is it there?
a. To rid the wet tank of alcohol that condenses and sets at the bottom
b. To eliminate the need for daily tank draining
c. To boost the tank pressure in the same way that turbo chargers boost engines
d. To reduce the risk of ice in air brake valves in cold weather
18. The brake pedal in an air brake system _________________.
a. Controls the speed of the air compressor
b. Is seldom used compared to hydraulic systems
c. Controls the air pressure applied to put on the brakes
d. Is connected to slack adjusters by a series of rods and linkages
19. If your truck or bus has dual parking control valves then you can use pressure from a separate tank for what purpose?
a. To balance the service brake system when you are parked.
b. To stay parked twice as long without using up the service air pressure.
c. To release the spring emergency and parking brakes to move a short distance.
d. To brake harder if the main tank is getting low.
20. If you must make an emergency stop than you should brake how?
a. So that you use the hand brake before the brake pedal
b. So that you do not need to worry about steering
c. So you can steer and so your vehicle stays in a straight line
d. So you can use the full power of the brakes to lock the wheels
21. To check the free play of manual slack adjusters of S-CAM brakes you should park on what kind of grade?
a. Level ground and apply the parking brake
b. Park on level ground, chock the wheels and release the parking brakes
c. Park on level ground, drain off the air pressure before checking the adjustment
d. Park on a slight grade, release the parking brakes and apply the service brake watching your vehicle movement
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22. The most important thing to do when a low air pressure warning comes on is what?
a. Up shift
b. Downshift
c. Adjust the brake pedal for more travel
d. Stop and safely park as soon as possible
23. What does the air compressor governor control?
a. The speed of the air compressor
b. Air pressure applied to the brakes
c. Air pumped into the air tanks
d. When the brake chambers release pressure
24. What describes the braking power of the spring brakes?
a. It increases when the service brakes are hot
b. It depends on the service brakes being in adjustment
c. It is not affected by the condition of the service brakes
d. It can only be tested by highly trained brake service people
25. All air brake equipped vehicles have what?
a. An air use gauge
b. A supply pressure gauge
c. At least one brake heater
d. A back-up hydraulic system
1 – (d) 6 – (b) 11 – (c) 16 – (c) 21 – (b)
2 – (a) 7 – (d) 12 – (c) 17 – (d) 22 – (d)
3 – (b) 8 – (d) 13 – (a) 18 – (c) 23 – (c)
4 – (b) 9 – (d) 14 – (b) 19 – (c) 24 – (b)
5 – (a) 10 – (a) 15 – (a) 20 – (c) 25 – (b)
Fourth set:
AIR BRAKES – FACT SHEET
CDL
- The air loss rate for a straight truck or bus with the engine off and the brakes on should not be more than 3 PSI in one minute.
- Your brakes are fading when you have to push harder on the brake pedal to control your speed on a downgrade.
- The supply pressure gauge shows how much pressure is in the air tanks.
- The brake system that applies and releases the brakes when the driver uses the brake pedal is the service brake system.
- If your vehicle has an alcohol evaporator, every day during cold weather you should check and fill the alcohol level.
- You should drain the water from compressed air tanks because water can freeze in cold weather and cause brake failure.
- To test service brakes, you should brake firmly when moving slowly forward. The brakes are O.K. if you do not notice a delayed
stopping action, an unusual feel, or the vehicle “pulls” to one side. - On long downhill grades, apply the brakes just enough to feel a slowdown. When your speed has been reduced to
approximately five miles per hour below your “safe” speed, release the brakes. When your speed has increased to your
safe speed, repeat steps one and two. Repeat this until you have reached the end of the downhill grade. - Your truck or bus has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do?
Stop right away and safely park. Continue only after the system is fixed. - During normal driving, spring brakes are usually held back by air pressure.
- Total stopping distance for air brakes is longer than that for hydraulic brakes due to brake lag.
- The most common type of foundation brake found on heavy vehicles is the S-CAM brake system.
- With air brake vehicles, the parking brake should be used whenever you leave the vehicle unattended.
- For emergency stab braking, you should press on the brake pedal as hard as you can, release the brakes when the wheels
lock, and when the wheels start rolling press the brakes fully again. - Parking or emergency brakes on trucks and buses can be held on by spring pressure.
- The driver must be able to see a low air pressure warning, which comes on when pressure in the air tanks fall below 60
PSI. - If your vehicle has an alcohol evaporator, it is there to reduce the risk of ice in air brake valves in cold weather.
- The brake pedal in an air brake system controls the air pressure applied to put on the brakes.
- If your truck or bus has dual parking control valves, you can use pressure from a separate tank to release the
emergency/parking brakes to move a short distance.
10 - To check the free play of manual slack adjusters of S-CAM brakes, you should park on level ground, chock the wheels, and
release the parking brake. - The most important thing to do when a low air pressure warning comes on is stop and safely park as soon as possible.
- The air compressor governor controls when air is pumped into the air tanks.
- The braking power of the spring brakes depends on the service brakes being in adjustment.
- All air brake equipped vehicles have a supply pressure gauge.
- If you must make an emergency stop, you should brake so you can steer and so your vehicle stays in a straight line.
- The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like spring
pressure. - A straight truck or bus air brake system should not leak at a rate of more than 2 PSI per minute with the engine off and the brakes
released. - Your vehicle has a dual air brake system. If a low air pressure warning comes on for the secondary system, you should bring the
vehicle to a safe stop and continue only when the system is fixed. - Air braking takes more time than hydraulic braking because air takes more time to flow through the lines than hydraulic fluid.
- Air brake systems combine three different systems. They are the service, parking, and the emergency brake systems.
- The application pressure gauge shows how much air pressure you are applying to the brakes.
- If you do not have automatic tank drains, you should drain the oil and water from the air storage tanks at the end of each
day of driving. - The proper method of braking when going down long and/or steep grades after selecting the proper gear is to brake your speed is about 5 miles per hour below your “safe” speed and then release your brakes.