Review Questions - Click On The Picture To Begin...
- 110 psi
- 125 psi
- 100 psi
- 115 psi
Quote From The CDL Manual:
Check air compressor governor cut-in and cut-out pressures: Pumping by the air compressor should start at about 100 psi and stop at about 125 psi. (Check manufacturer's specifications.) Run the engine at a fast idle. The air governor should cut out the air compressor at about the manufacturer's specified pressure. The air pressure shown by your gauge(s) will stop rising. With the engine idling, step on and off the brake to reduce the air tank pressure. The compressor should cut in at about the manufacturer's specified cut-in pressure. The pressure should begin to rise.
- None of these answers are correct
- The loss rate should be less than 1 psi in 1 minute for single vehicles and less than 2 psi in 1 minute for combination vehicles
- The loss rate should be less than 3 psi in 1 minute for single vehicles and less than 4 psi in 1 minute for combination vehicles
- The loss rate should be less than 3 psi in 2 minutes for single vehicles and less than 4 psi in 2 minutes for combination vehicles
Quote From The CDL Manual:
Test air leakage rate: With a fully-charged air system (typically 125 psi), turn off the engine, release the service brake, and time the air pressure drop. The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles. Then apply 90 psi or more with the brake pedal. After the initial pressure drop, if the air pressure falls more than 3 psi in 1 minute for single vehicles and more than 4 psi for combination vehicles, the air loss rate is too much. Check for air leaks, and repair before driving the vehicle. Otherwise, you could lose your brakes while driving.
TruckingTruth's Advice:
You really need to memorize the allowable air leakage rates. This will very likely come up on your written exam and will come up again during the pre-trip exam. Here's what you should memorize (create flash cards if you have to).
With the service brakes released (not depressing the brake pedal):
- Air loss rate should be less than 2 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 3 psi in 1 minute for combination vehicles (vehicles with a trailer).
With the service brakes depressed (pressing the brake pedal):
- Air loss rate should be less than 3 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 4 psi in 1 minute for combination vehicles (vehicles with a trailer).
Be sure to have that memorized. Very important!!
- No more than 3 psi in 1 minute
- No more than 6 psi in 1 minute
- No more than 5 psi in 1 minute
- No more than 4 psi in 1 minute
Quote From The CDL Manual:
Test air leakage rate: With a fully-charged air system (typically 125 psi), turn off the engine, release the service brake, and time the air pressure drop. The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles. Then apply 90 psi or more with the brake pedal. After the initial pressure drop, if the air pressure falls more than 3 psi in 1 minute for single vehicles and more than 4 psi for combination vehicles, the air loss rate is too much. Check for air leaks, and repair before driving the vehicle. Otherwise, you could lose your brakes while driving.
TruckingTruth's Advice:
You really need to memorize the allowable air leakage rates. This will very likely come up on your written exam and will come up again during the pre-trip exam. Here's what you should memorize (create flash cards if you have to).
With the service brakes released (not depressing the brake pedal):
- Air loss rate should be less than 2 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 3 psi in 1 minute for combination vehicles (vehicles with a trailer).
With the service brakes depressed (pressing the brake pedal):
- Air loss rate should be less than 3 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 4 psi in 1 minute for combination vehicles (vehicles with a trailer).
Be sure to have that memorized. Very important!!
- You could encounter steering difficulties
- The air system may not keep enough air pressure for safe driving
- All of these answers are correct
- You may get increased condensation in your air tanks
Quote From The CDL Manual:
Check air compressor governor cut-in and cut-out pressures:
Pumping by the air compressor should start at about 100 psi and stop at about 125 psi (check manufacturer?s specifications). Run the engine at a fast idle. The air governor should cut out the air compressor at about the manufacturer?s specified pressure. The air pressure shown by your gauge(s) will stop rising. With the engine idling, step on and off the brake to reduce the air tank pressure. The compressor should cut in at about the manufacturer?s specified cut-in pressure. The pressure should begin to rise.
If the air governor does not work as described above, it may need to be repaired. A governor that does not work right may not keep enough air pressure for safe driving.
TruckingTruth's Advice:
It is important to memorize the "cut in" and "cut out" levels for the air governor as well as the terminology.
Cut in: When the governor tells the air compressor to start pumping air into the air tanks. This should occur when air pressure falls to about 100 psi.
Cut out: When the governor tells the air compressor to stop pumping air into the air tanks. This should occur when the air pressure has risen to about 125 psi.
- None of these answers are correct
- The loss rate should be less than 4 psi in 1 minute for single vehicles and less than 5 psi in 1 minute for combination vehicles
- The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles
- The loss rate should be less than 3 psi in 2 minutes for single vehicles and less than 4 psi in 2 minutes for combination vehicles
Quote From The CDL Manual:
Test air leakage rate: With a fully-charged air system (typically 125 psi), turn off the engine, release the service brake, and time the air pressure drop. The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles. Then apply 90 psi or more with the brake pedal. After the initial pressure drop, if the air pressure falls more than 3 psi in 1 minute for single vehicles and more than 4 psi for combination vehicles, the air loss rate is too much. Check for air leaks, and repair before driving the vehicle. Otherwise, you could lose your brakes while driving.
TruckingTruth's Advice:
You really need to memorize the allowable air leakage rates. This will very likely come up on your written exam and will come up again during the pre-trip exam. Here's what you should memorize (create flash cards if you have to).
With the service brakes released (not depressing the brake pedal):
- Air loss rate should be less than 2 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 3 psi in 1 minute for combination vehicles (vehicles with a trailer).
With the service brakes depressed (pressing the brake pedal):
- Air loss rate should be less than 3 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 4 psi in 1 minute for combination vehicles (vehicles with a trailer).
Be sure to have that memorized. Very important!!
- Less than 2 psi in 1 minute
- Less than 3 psi in 1 minute
- Less than 4 psi in 1 minutes
- Less than 1 psi in 1 minute
Quote From The CDL Manual:
Test air leakage rate: With a fully-charged air system (typically 125 psi), turn off the engine, release the service brake, and time the air pressure drop. The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles. Then apply 90 psi or more with the brake pedal. After the initial pressure drop, if the air pressure falls more than 3 psi in 1 minute for single vehicles and more than 4 psi for combination vehicles, the air loss rate is too much. Check for air leaks, and repair before driving the vehicle. Otherwise, you could lose your brakes while driving.
TruckingTruth's Advice:
You really need to memorize the allowable air leakage rates. This will very likely come up on your written exam and will come up again during the pre-trip exam. Here's what you should memorize (create flash cards if you have to).
With the service brakes released (not depressing the brake pedal):
- Air loss rate should be less than 2 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 3 psi in 1 minute for combination vehicles (vehicles with a trailer).
With the service brakes depressed (pressing the brake pedal):
- Air loss rate should be less than 3 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 4 psi in 1 minute for combination vehicles (vehicles with a trailer).
Be sure to have that memorized. Very important!!
- No more than 4 psi in 1 minute
- No more than 1 psi in 1 minute
- No more than 2 psi in 1 minute
- No more than 3 psi in 1 minute
Quote From The CDL Manual:
Test air leakage rate: With a fully-charged air system (typically 125 psi), turn off the engine, release the service brake, and time the air pressure drop. The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles. Then apply 90 psi or more with the brake pedal. After the initial pressure drop, if the air pressure falls more than 3 psi in 1 minute for single vehicles and more than 4 psi for combination vehicles, the air loss rate is too much. Check for air leaks, and repair before driving the vehicle. Otherwise, you could lose your brakes while driving.
TruckingTruth's Advice:
You really need to memorize the allowable air leakage rates. This will very likely come up on your written exam and will come up again during the pre-trip exam. Here's what you should memorize (create flash cards if you have to).
With the service brakes released (not depressing the brake pedal):
- Air loss rate should be less than 2 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 3 psi in 1 minute for combination vehicles (vehicles with a trailer).
With the service brakes depressed (pressing the brake pedal):
- Air loss rate should be less than 3 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 4 psi in 1 minute for combination vehicles (vehicles with a trailer).
Be sure to have that memorized. Very important!!
- 100 psi
- 110 psi
- 115 psi
- 125 psi
Quote From The CDL Manual:
Check air compressor governor cut-in and cut-out pressures: Pumping by the air compressor should start at about 100 psi and stop at about 125 psi. (Check manufacturer's specifications.) Run the engine at a fast idle. The air governor should cut out the air compressor at about the manufacturer's specified pressure. The air pressure shown by your gauge(s) will stop rising. With the engine idling, step on and off the brake to reduce the air tank pressure. The compressor should cut in at about the manufacturer's specified cut-in pressure. The pressure should begin to rise.
- About 115 psi
- About 90 psi
- About 125 psi
- About 110 psi
Quote From The CDL Manual:
Check air compressor governor cut-in and cut-out pressures: Pumping by the air compressor should start at about 100 psi and stop at about 125 psi. (Check manufacturer's specifications.) Run the engine at a fast idle. The air governor should cut out the air compressor at about the manufacturer's specified pressure. The air pressure shown by your gauge(s) will stop rising. With the engine idling, step on and off the brake to reduce the air tank pressure. The compressor should cut in at about the manufacturer's specified cut-in pressure. The pressure should begin to rise.
TruckingTruth's Advice:
It is important to memorize the "cut in" and "cut out" levels for the air governor as well as the terminology.
Cut in: When the governor tells the air compressor to start pumping air into the air tanks. This should occur when air pressure falls to about 100 psi.
Cut out: When the governor tells the air compressor to stop pumping air into the air tanks. This should occur when the air pressure has risen to about 125 psi.
- Within 25 seconds
- Within 45 seconds
- Within 30 seconds
- Within 1 minute
Quote From The CDL Manual:
Check rate of air pressure buildup: When the engine is at operating RPM, the pressure should build from 85 to 100 psi within 45 seconds in dual air systems. (If the vehicle has larger than minimum air tanks, the buildup time can be longer and still be safe. Check the manufacturer's specifications.) In single air systems pre-1975), typical requirements are pressure build-up from 50 to 90 psi within 3 minutes with the engine at an idle speed of 600-900 RPM.
- Less than 4 psi in 1 minute for single vehicles and more than 3 psi for combination vehicles
- Less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles
- Less than 3 psi in 1 minute for single vehicles and more than 4 psi for combination vehicles
- Less than 3 psi in 1 minute for single vehicles and less than 2 psi in 1 minute for combination vehicles
Quote From The CDL Manual:
Test air leakage rate: With a fully-charged air system (typically 125 psi), turn off the engine, release the service brake, and time the air pressure drop. The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles. Then apply 90 psi or more with the brake pedal. After the initial pressure drop, if the air pressure falls more than 3 psi in 1 minute for single vehicles and more than 4 psi for combination vehicles, the air loss rate is too much. Check for air leaks, and repair before driving the vehicle. Otherwise, you could lose your brakes while driving.
TruckingTruth's Advice:
You really need to memorize the allowable air leakage rates. This will very likely come up on your written exam and will come up again during the pre-trip exam. Here's what you should memorize (create flash cards if you have to).
With the service brakes released (not depressing the brake pedal):
- Air loss rate should be less than 2 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 3 psi in 1 minute for combination vehicles (vehicles with a trailer).
With the service brakes depressed (pressing the brake pedal):
- Air loss rate should be less than 3 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 4 psi in 1 minute for combination vehicles (vehicles with a trailer).
Be sure to have that memorized. Very important!!
- Less than 1 psi in 1 minute
- There should be no loss of any psi in 1 minute
- Less than 2 psi in 1 minute
- Less than 3 psi in 1 minute
Quote From The CDL Manual:
Test air leakage rate: With a fully-charged air system (typically 125 psi), turn off the engine, release the service brake, and time the air pressure drop. The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles. Then apply 90 psi or more with the brake pedal. After the initial pressure drop, if the air pressure falls more than 3 psi in 1 minute for single vehicles and more than 4 psi for combination vehicles, the air loss rate is too much. Check for air leaks, and repair before driving the vehicle. Otherwise, you could lose your brakes while driving.
TruckingTruth's Advice:
You really need to memorize the allowable air leakage rates. This will very likely come up on your written exam and will come up again during the pre-trip exam. Here's what you should memorize (create flash cards if you have to).
With the service brakes released (not depressing the brake pedal):
- Air loss rate should be less than 2 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 3 psi in 1 minute for combination vehicles (vehicles with a trailer).
With the service brakes depressed (pressing the brake pedal):
- Air loss rate should be less than 3 psi in 1 minute for a single vehicle.
- Air loss rate should be less than 4 psi in 1 minute for combination vehicles (vehicles with a trailer).
Be sure to have that memorized. Very important!!
- 80 psi
- None of these are correct
- 120 psi
- 100 psi
Quote From The CDL Manual:
Test low pressure warning signal: Shut the engine off when you have enough air pressure that the low-pressure warning signal is not on. Turn the electrical power on, and step on and off the brake pedal to reduce air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 60 psi in the air tank, or the tank with the lowest air pressure in dual air systems.
If the warning signal does not work, you could lose air pressure and not know it. This could cause sudden emergency braking in a single circuit air system. In dual systems the stopping distance will be increased. Only limited braking can be done before the spring brakes come on.
TruckingTruth's Advice:
It is very important to know how to check the low pressure warning signal. You will learn most of the procedure when studying for the pre-trip exam, but for the written exam, here's what you should know:
- Build air pressure so the warning light and buzzer are not activated.
- Turn the engine off.
- Turn the key to the "on" position (this will allow you to see the warning light and see the buzzer).
- Begin depressing and releasing the service brake (brake pedal) repeatedly. This will deplete your air pressure and at about 60 psi, the warning light and buzzer should activate.
- Idle the vehicle in the lowest gear possible then apply the parking brake and be sure the vehicle comes to a complete stop
- Stop the vehicle, put the parking brake on, and pull against it in the highest gear
- Place chocks against the tires of the truck, release the parking brake, then visually inspect each parking brake
- Stop the vehicle, put the parking brake on, and gently pull against it in a low gear to test that the parking brake will hold
Quote From The CDL Manual:
Test parking brake: Stop the vehicle, put the parking brake on, and gently pull against it in a low gear to test that the parking brake will hold.
- When the governor tells the air compressor to start pumping air into the air tanks
- When the governor tells the emergency brakes to engage
- When the governor tells the service brakes to activate
- When the governor tells the air compressor to stop pumping air into the air tanks
Quote From The CDL Manual:
Check air compressor governor cut-in and cut-out pressures: Pumping by the air compressor should start at about 100 psi and stop at about 125 psi. (Check manufacturer's specifications.) Run the engine at a fast idle. The air governor should cut out the air compressor at about the manufacturer's specified pressure. The air pressure shown by your gauge(s) will stop rising. With the engine idling, step on and off the brake to reduce the air tank pressure. The compressor should cut in at about the manufacturer's specified cut-in pressure. The pressure should begin to rise.
TruckingTruth's Advice:
It is important to memorize the "cut in" and "cut out" levels for the air governor as well as the terminology.
Cut in: When the governor tells the air compressor to start pumping air into the air tanks. This should occur when air pressure falls to about 100 psi.
Cut out: When the governor tells the air compressor to stop pumping air into the air tanks. This should occur when the air pressure has risen to about 125 psi.
- Move the vehicle forward slowly (about 5 mph) and apply the brakes firmly using the brake pedal, making note of any unusual stopping action
- Service brakes should only be tested by a certified mechanic
- Bring the vehicle to highway speed (about 55 mph), check for traffic behind you, and if no traffic is present depress the brakes firmly for about 1 second making note of any unusual stopping action
- Chock the wheels, turn off the engine, then release all brakes to perform a manual inspection of the service brakes
Quote From The CDL Manual:
Test service brakes: Wait for normal air pressure, release the parking brake, move the vehicle forward slowly (about 5 mph) and apply the brakes firmly using the brake pedal. Note any vehicle "pulling" to one side, unusual feel or delayed stopping action.
This test may show you problems that you otherwise would not know about until you needed the brakes on the road.
TruckingTruth's Advice:
You will be expected to perform a service brake check during your pre-trip examination.
- Chock the wheels, turn the engine off, release all brakes, then step on and off the brake pedal to deplete air in the system until the emergency brakes activate
- With the engine running and the parking brake on, step on and off the brake pedal to deplete air in the system until the emergency brakes activate
- With your foot on the service brake, engage and release the parking brake until air is depleted enough for the emergency brake valve to pop out
- Chock the wheels, turn the engine off, release all brakes, then disconnect a brake line and allow the air to deplete which will show if the spring brakes activate automatically
Quote From The CDL Manual:
Check that spring brakes come on automatically: Chock the wheels, release the parking brakes when you have enough air pressure to do it and shut the engine off. Step on and off the brake pedal to reduce the air tank pressure. The "parking brake" knob should pop out when the air pressure falls to the manufacturer's specification, usually in a range between 20 and 40 psi. This causes the spring brakes to come on.
- Step 3: The low air-pressure warning signal must come on before the pressure drops to less than 60 psi in the air tank, or the tank with the lowest air pressure in dual air systems
- Step 2: Turn the electrical power on, and step on and off the brake pedal to reduce air tank pressure
- All of these steps are correct
- Step 1: Shut the engine off when you have enough air pressure that the low-pressure warning signal is not on
Quote From The CDL Manual:
Test low pressure warning signal: Shut the engine off when you have enough air pressure that the low-pressure warning signal is not on. Turn the electrical power on, and step on and off the brake pedal to reduce air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 60 psi in the air tank, or the tank with the lowest air pressure in dual air systems.
TruckingTruth's Advice:
It is very important to know how to check the low pressure warning signal. You will learn most of the procedure when studying for the pre-trip exam, but for the written exam, here's what you should know:
- Build air pressure so the warning light and buzzer are not activated.
- Turn the engine off.
- Turn the key to the "on" position (this will allow you to see the warning light and see the buzzer).
- Begin depressing and releasing the service brake (brake pedal) repeatedly. This will deplete your air pressure and at about 60 psi, the warning light and buzzer should activate.
- 90 psi
- 100 psi
- 110 psi
- 120 psi
Quote From The CDL Manual:
Check air compressor governor cut-in and cut-out pressures: Pumping by the air compressor should start at about 100 psi and stop at about 125 psi. (Check manufacturer's specifications.) Run the engine at a fast idle. The air governor should cut out the air compressor at about the manufacturer's specified pressure. The air pressure shown by your gauge(s) will stop rising. With the engine idling, step on and off the brake to reduce the air tank pressure. The compressor should cut in at about the manufacturer's specified cut-in pressure. The pressure should begin to rise.
TruckingTruth's Advice:
It is important to memorize the "cut in" and "cut out" levels for the air governor as well as the terminology.
Cut in: When the governor tells the air compressor to start pumping air into the air tanks. This should occur when air pressure falls to about 100 psi.
Cut out: When the governor tells the air compressor to stop pumping air into the air tanks. This should occur when the air pressure has risen to about 125 psi.
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