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Minnesota CDL Air Brakes Test Practice Questions - Minnesota Commercial Driver License (CDL) Air Brakes Knowledge Test Exam
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Question
1
of 25
QUESTION 1 / 25
What part pumps compressed air into a vehicle's air storage tanks?
Choose one answer below.
A
Air compressor
✓
B
Brake chamber
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C
Slack adjuster
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D
Alcohol evaporator
✓
QUESTION 2 / 25
What does the air compressor governor control?
Choose one answer below.
A
When the compressor pumps air into the tanks
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B
How thick the brake lining is
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C
Whether ABS is turned on
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D
The amount of fuel in the engine
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QUESTION 3 / 25
Why must air tanks be drained?
Choose one answer below.
A
To remove water and compressor oil
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B
To add brake fluid
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C
To test tire tread depth
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D
To make ABS cycle
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QUESTION 4 / 25
When should manually drained air tanks normally be drained?
Choose one answer below.
A
At the end of each day of driving
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B
Only once a year
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C
Only after the low-air warning comes on
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D
Only before a road test
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QUESTION 5 / 25
What should a driver do if the low-air warning activates while driving?
Choose one answer below.
A
Stop safely as soon as possible and have the problem fixed
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B
Continue normally if the truck still moves
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C
Fan the brakes to silence the warning
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D
Pull the parking brake immediately at highway speed
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QUESTION 6 / 25
How are spring parking brakes held in the released position?
Choose one answer below.
A
By air pressure compressing the spring
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B
By brake fluid pressure
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C
By ABS wheel sensors
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D
By engine oil pressure
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QUESTION 7 / 25
Which control normally applies the parking brakes on a straight truck or bus with air brakes?
Choose one answer below.
A
The yellow parking-brake knob
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B
The red trailer-air-supply knob
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C
The windshield wiper switch
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D
The ABS malfunction lamp
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QUESTION 8 / 25
What is the main purpose of a dual air brake system?
Choose one answer below.
A
To keep separate primary and secondary air circuits so one failure does not remove all braking
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B
To make the truck use both diesel and gasoline
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C
To remove the need for air gauges
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D
To replace spring brakes with hydraulic brakes
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QUESTION 9 / 25
What is the purpose of ABS on an air-brake vehicle?
Choose one answer below.
A
To help prevent wheel lockup during hard braking
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B
To shorten every stop on every surface
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C
To replace the service brakes
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D
To build air pressure faster
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QUESTION 10 / 25
What is brake lag?
Choose one answer below.
A
The delay between pressing the pedal and the brakes applying fully
✓
B
A low-fuel warning
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C
The time it takes to drain air tanks
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D
A method for adjusting slack adjusters
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QUESTION 11 / 25
For a normal stop with air brakes, what should you do?
Choose one answer below.
A
Apply steady pressure to the brake pedal
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B
Pump the pedal repeatedly
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C
Use only the parking brake
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D
Turn off the engine
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QUESTION 12 / 25
What does a brake chamber do?
Choose one answer below.
A
Changes air pressure into mechanical pushrod force
✓
B
Stores fuel for the compressor
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C
Drains water from the tanks
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D
Warns of low air pressure
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QUESTION 13 / 25
What is a slack adjuster used for on an S-cam brake?
Choose one answer below.
A
It transfers pushrod force to rotate the S-cam
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B
It stores compressed air
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C
It dries moisture from the air
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D
It sets the speed limiter
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QUESTION 14 / 25
During an air-brake inspection, why should the driver watch both air gauges on a dual system?
Choose one answer below.
A
Each gauge shows pressure in a separate air circuit
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B
One gauge shows engine coolant temperature
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C
Both gauges are only for the trailer
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D
The gauges show brake lining thickness
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QUESTION 15 / 25
Why is moisture in an air brake system especially dangerous in Minnesota winter conditions?
Choose one answer below.
A
It can freeze and block valves or lines
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B
It makes tires wider
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C
It turns ABS off permanently
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D
It increases fuel octane
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QUESTION 16 / 25
What was the front brake limiting valve found on some older vehicles intended to do?
Choose one answer below.
A
Reduce front-wheel braking force under certain conditions
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B
Increase compressor cut-out pressure
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C
Drain the wet tank automatically
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D
Turn ABS on and off
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QUESTION 17 / 25
In Minnesota CDL restriction codes, what does an L restriction mean?
Choose one answer below.
A
Not valid for CMVs with air brakes
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B
Only valid for tank vehicles
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C
Must drive only automatic transmissions
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D
Hazardous materials only
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QUESTION 18 / 25
About what pressure is the usual governor cut-out level in the CDL manual?
Choose one answer below.
A
Around 125 psi
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B
Around 30 psi
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C
Around 55 psi
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D
Around 300 psi
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QUESTION 19 / 25
About what pressure is the usual governor cut-in level in the CDL manual?
Choose one answer below.
A
Around 100 psi
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B
Around 20 psi
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C
Around 150 psi
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D
Around 5 psi
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QUESTION 20 / 25
Where do water and oil usually collect in the air-brake system?
Choose one answer below.
A
At the bottom of the air tanks
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B
Inside the steering wheel
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C
In the tire sidewalls
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D
On the ABS dashboard lamp
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QUESTION 21 / 25
What devices commonly warn the driver about low air pressure?
Choose one answer below.
A
A warning light, buzzer, or mechanical wig-wag
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B
A fuel cap click
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C
A tire pressure pencil gauge only
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D
A cargo seal
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QUESTION 22 / 25
What happens if air pressure is lost from spring brakes?
Choose one answer below.
A
The springs apply the brakes
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B
The brakes become permanently stronger service brakes
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C
The ABS builds air pressure
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D
The brake drums disappear
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QUESTION 23 / 25
What should you do if an air-brake inspection finds an unsafe leak?
Choose one answer below.
A
Have it repaired before driving
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B
Drive only at night
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C
Ignore it if the compressor can keep up
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D
Cover the gauge so it is not distracting
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QUESTION 24 / 25
If the ABS warning lamp stays on after the system check, what does it mean?
Choose one answer below.
A
The ABS may have a fault and needs service
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B
The service brakes are gone
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C
The air tanks are full of alcohol
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D
The parking brake is automatically released
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QUESTION 25 / 25
What is the best way to control speed before a long downgrade?
Choose one answer below.
A
Select a low gear before starting down
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B
Shift to neutral to coast
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C
Use only the parking brakes
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D
Wait until brakes fade, then downshift
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