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Free Practice Questions for ND CDL Air Brakes

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Sample ND CDL Air Brakes Practice Questions

Try these sample questions to review concepts for the ND CDL Air Brakes exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 220+ question experience with AI tutoring.

1A trainee in Fargo calls air brakes 'one system.' The North Dakota manual instead describes three systems working together. Which three?
A.Service, parking, and engine-retarder systems
B.Primary, secondary, and trailer-supply systems
C.Service, parking, and emergency systems
D.Spring, wedge, and disc systems
Explanation: Section 5 lists the service brake (applied with the pedal in normal driving), the parking brake (applied with the parking control), and the emergency brake. The emergency system uses parts of the service and parking systems to stop the vehicle if the brake system fails.
2A mechanic says the governor on your bus may be faulty. What job does that part normally perform?
A.It controls when the air compressor pumps air into the storage tanks
B.It cuts the air pressure to the front brakes on slippery roads
C.It releases tank pressure when pressure climbs too high
D.It sets how much air pressure reaches the brake chambers each time the pedal is pressed
Explanation: Section 5.1.2 says the governor controls when the compressor pumps air into the storage tanks. It stops pumping at the cut-out level and lets the compressor pump again at the cut-in level.
3Your tanks bled down overnight in a Minot cold snap. As pressure falls, at roughly what reading does Section 5.1.2 say the compressor is put back to work?
A.About 60 psi
B.About 125 psi
C.About 150 psi
D.About 100 psi
Explanation: The governor stops the compressor at the cut-out level, around 125 psi. When tank pressure falls to the cut-in level, around 100 psi, the governor lets the compressor pump again.
4Section 5.1.2 gives a governor cut-out of about 125 psi and a cut-in of about 100 psi. About how far does tank pressure fall from cut-out before the compressor starts pumping again?
A.About 40 psi
B.About 25 psi
C.About 65 psi
D.About 100 psi
Explanation: The compressor stops at about 125 psi and starts again at about 100 psi, so pressure drops about 125 - 100 = 25 psi before pumping resumes. Always check the manufacturer's specifications for the actual settings.
5Why must the water and oil that collect in air tanks be drained?
A.They lower the governor's cut-out pressure
B.Water can freeze in cold weather and cause brake failure
C.They make the low air warning come on too early
D.They push tank pressure above the safety relief valve's opening setting
Explanation: Section 5.1.4 says compressed air usually carries some water and compressor oil, which is bad for the air brake system. The water can freeze in cold weather and cause brake failure, so the tanks must be drained completely.
6How is a manually operated air tank drain opened, and how often should you drain the tank yourself?
A.By pressing a dash button, once a week
B.By a quarter turn or by pulling a cable, after every brake application
C.By removing the tank plug, only when the warning light comes on
D.By a quarter turn or a pulled cable, at the end of each driving day
Explanation: Section 5.1.4 says manual drains are opened by turning a quarter turn or by pulling a cable, and you must drain the tanks yourself at the end of each day of driving.
7Your bus's automatic tank drains have built-in electric heaters. Why do some automatic drains come with them?
A.To keep the automatic drain from freezing in cold weather
B.To dry the air before it reaches the compressor
C.To warm the brake drums and linings before a cold-weather start
D.To heat the alcohol in the alcohol evaporator
Explanation: Section 5.1.4 says automatic drains expel water and oil on their own, and some come with electric heating devices that help keep the automatic drain from freezing in cold weather.
8A coworker asks why there is an alcohol container plumbed into the bus's air system. What is that evaporator for?
A.It removes compressor oil from the air
B.It replaces the need to drain the air tanks during cold weather
C.It adds alcohol to the air to cut the risk of ice in the valves
D.It cools the compressor on long climbs
Explanation: Section 5.1.5 says an alcohol evaporator puts alcohol into the air system. This reduces the risk of ice in air brake valves and other parts during cold weather, because ice inside the system can stop the brakes from working.
9During a North Dakota cold snap, you drive a bus with an alcohol evaporator and manual tank drains. Which routine follows Section 5.1.5?
A.Fill the evaporator weekly and skip tank draining while it is in use
B.Drain the tanks weekly and fill the evaporator only when ice appears
C.Fill the evaporator once a season and drain the tanks monthly
D.Check and fill the alcohol container every day, and still drain the tanks daily
Explanation: Section 5.1.5 says to check the alcohol container and fill it as needed every day during cold weather. Daily tank draining is still needed to get rid of water and oil unless the system has automatic drain valves.
10Suppose the governor sticks and air pressure keeps climbing. Which valve protects the system, where is it, and when does it usually open?
A.In the last air tank, at about 100 psi
B.In the first tank the compressor fills, at about 150 psi
C.At the brake pedal, at about 60 psi
D.On the governor itself, at about the 125 psi cut-out level
Explanation: Section 5.1.6 says a safety relief valve is installed in the first tank the compressor pumps air to. It protects the tank and the rest of the system from too much pressure and is usually set to open at 150 psi.

About the ND CDL Air Brakes Exam

The North Dakota CDL Air Brakes knowledge test is the NDDOT test for drivers of vehicles with air brakes, including air over hydraulic brakes. North Dakota does not treat air brakes as an endorsement; drivers who do not pass the knowledge test and test in an air-braked vehicle get the L or Z restriction. NDDOT gives the test in English only, and it is based on Section 5 of the North Dakota CDL Manual: system parts, spring brakes, ABS, dual systems, inspection checks, and safe braking. Independent practice by OpenExamPrep offers four-option study questions with explanations that follow the manual's Section 5 figures, including its 60 psi low air warning. These multiple-choice questions are a study aid, not a copy or simulation of the official test, and they do not replace hands-on training or the skills test.

Exam sponsor: North Dakota Department of Transportation (NDDOT), Driver License Division. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

A knowledge test at an NDDOT driver license site based on Section 5 of the North Dakota CDL Manual, required for any vehicle with air brakes, including air over hydraulic brakes. Applicants who fail it, or who take the skills test without air brakes, get the L restriction; testing with air-over-hydraulic brakes gives the Z restriction. On the skills test, the air brake check is an automatic-fail part of the vehicle inspection.

Time Limit

Not published by NDDOT

Passing Score

At least 80% correct on each knowledge test (49 CFR 383.135)

Exam / Certification Fees

$5 per knowledge test attempt; $15 commercial learner's permit ($20 non-domiciled); $5 road test

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

Manual Sections 5.1.1 to 5.1.13 (official weight not published)

Air Brake System Parts

Compressor, governor, tanks and drains, alcohol evaporator, safety valve, brake pedal, foundation brakes, gauges, the low air warning, the stop light switch, and front brake limiting valves.

Manual Sections 5.1.14, 5.1.15, and 5.4.8 (official weight not published)

Spring Brakes and Parking Controls

Spring brake pressures, parking controls, modulating and dual parking control valves, and parking with hot or wet brakes.

Manual Sections 5.1.16 and 5.4.2 (official weight not published)

Antilock Brakes

ABS dates, the malfunction lamp, and braking with ABS.

Manual Section 5.2 (official weight not published)

Dual Air Brake Systems

Primary and secondary systems, minimum pressure before driving, the warning signal, and losing pressure in one system.

Manual Section 5.3 (official weight not published)

Inspecting Air Brakes

Slack adjusters, drums and linings, the warning and spring brake tests, buildup rates, leakage limits, governor checks, and brake tests.

Manual Section 5.4 (official weight not published)

Using Air Brakes

Normal and emergency stops, brake lag and stopping distance, brake fade, downgrade braking, and low air pressure.

Manual Section 1.1.1, NDDOT rules, and 49 CFR 383.95 and 383.135 (official weight not published)

Testing and Restrictions

Who must test, the passing score, L and Z restrictions, fees, and the air brake check on the skills test.

Preparing for the ND CDL Air Brakes Exam

What You Need to Know

  • Passing score: At least 80% correct on each knowledge test (49 CFR 383.135)
  • Assessment: A knowledge test at an NDDOT driver license site based on Section 5 of the North Dakota CDL Manual, required for any vehicle with air brakes, including air over hydraulic brakes. Applicants who fail it, or who take the skills test without air brakes, get the L restriction; testing with air-over-hydraulic brakes gives the Z restriction. On the skills test, the air brake check is an automatic-fail part of the vehicle inspection.
  • Time limit: Not published by NDDOT
  • Exam / certification fees: $5 per knowledge test attempt; $15 commercial learner's permit ($20 non-domiciled); $5 road test Official sources

Using Our Practice Resources

  • Work through all 220 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

ND CDL Air Brakes: Suggested Study Strategy

1Memorize Section 5's pressure figures: cut-in about 100 psi, cut-out about 125 psi, safety valve about 150 psi, low air warning before 60 psi, and spring brakes at 20 to 45 psi.
2Learn the leakage limits as a pair of pairs: released 2 and 3 psi, applied 3 and 4 psi, for single and combination vehicles.
3Practice the brake lag math: 142 + 61 + 32 + 216 feet is about 451 feet at 55 mph.
4Know the restrictions: L for testing without air brakes, Z for air-over-hydraulic brakes.

Frequently Asked Questions

Is the air brake test an endorsement in North Dakota?

No. NDDOT says North Dakota does not classify air brakes as an endorsement. Instead, it restricts the CDL to 'No Airbrake Equipped CMV' (L) or 'No Full Airbrake Equipped CMV' (Z) unless the driver passes both a knowledge test and a road test in an air-braked vehicle.

What happens if I take my road test in a vehicle without air brakes?

Your license gets the L restriction, which bars you from driving a commercial vehicle with any type of air brakes (49 CFR 383.95). Testing in a vehicle with air-over-hydraulic brakes gives the Z restriction instead.

What are the air leakage limits?

Section 5.3.3 says that with the engine off and the parking brake released, air loss should be less than 2 psi in one minute for single vehicles and less than 3 psi for combinations. With the brakes applied (90 psi or more), a loss of more than 3 psi (single) or 4 psi (combination) in one minute after the initial drop is too much.

At what pressure must the low air warning come on?

Section 5 of the North Dakota CDL Manual says the warning must come on before tank pressure falls below 60 psi (or one-half the governor cut-out pressure on older vehicles), and large buses commonly signal at 80-85 psi. North Dakota's modernized skills test check (Section 11M) uses 55 psi, so follow the manufacturer's specification for your test vehicle.

When do spring brakes come on?

Section 5.1.14 says tractor and straight truck spring brakes come fully on when air pressure drops to 20 to 45 psi, typically 20 to 30 psi. Stop safely as soon as the low air warning comes on rather than waiting for them.

How should I brake on a long downgrade?

Get into the proper low gear before the grade. Once at your safe speed, brake hard enough to feel a definite slowdown until you are about 5 mph below the safe speed (about three seconds), release, and repeat when you are back at the safe speed.

Are these practice questions the same as the official test?

No. They are independent four-option study questions written from Section 5 of the North Dakota CDL Manual and NDDOT rules. They help you review the material but are not a copy or simulation of the NDDOT test.