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Key Facts: ME CDL Air Brakes Exam

80%

Passing score required on each CDL knowledge test

49 CFR 383.135

55 psi

Pressure the low air warning must come on before

Maine CDL Manual, Section 5.1.11

20 to 45 psi

Range in which tractor and straight truck spring brakes come fully on

Maine CDL Manual, Section 5.1.14

4 parts

Parts of the skills-test air brake check; missing any is an automatic failure

Maine CDL Manual, Section 11.1.2

32 ft

Distance air brake lag adds at 55 mph on dry pavement

Maine CDL Manual, Section 5.4.4

Maine's CDL Air Brakes knowledge test requires 80% to pass; the BMV does not publish its question count or time limit. Key figures from the Maine CDL Manual: governor cut-in about 100 psi and cut-out about 125 psi (120 to 140 psi in the skills-test check), low air warning before 55 psi, spring brakes at 20 to 45 psi, and leakage limits of under 2 vs. 3 psi per minute released and 3 vs. 4 psi applied (single vs. combination).

Sample ME CDL Air Brakes Practice Questions

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

1Which set names the three braking systems that Section 5 of the Maine CDL Manual says make up an air brake system?
A.Primary, secondary, and trailer systems
B.Service, retarder, and parking systems
C.Service, parking, and emergency systems
D.Foundation, spring, and antilock systems
Explanation: Section 5 says air brakes are really three different braking systems: the service brake (applied with the pedal in normal driving), the parking brake (applied with the parking brake control), and the emergency brake system, which uses parts of the service and parking systems to stop the vehicle if the brake system fails.
2In an air brake system, what does the emergency brake system use to stop the vehicle if the brake system fails?
A.Parts of the service and parking brake systems
B.A separate hydraulic circuit on the front axle
C.The engine retarder and the exhaust brake
D.A dedicated third air tank used only in emergencies
Explanation: Section 5 says the emergency brake system uses parts of the service and parking brake systems to stop the vehicle in a brake system failure. Spring brakes, held off by air pressure, are usually how this need is met.
3On a town plow truck's engine compartment check, you find that the air compressor is not lubricated by engine oil but has a separate oil reservoir. Under Section 5.1.1, what is your job?
A.Leave it alone; only a mechanic may check a separate compressor reservoir
B.Bleed off its oil whenever you drain the air tanks
C.Check it only if the governor fails to cut out
D.Check its oil level before you drive
Explanation: Section 5.1.1 explains that an air compressor is either lubricated by engine oil or has an oil supply of its own. When it has its own supply, the driver checks that oil level before driving. Because the compressor is driven by the engine through gears or a v-belt, Section 5.3.1 also has you check a belt-driven compressor's belt during Step 2.
4In an air brake system, what does the air compressor governor control?
A.How much air pressure reaches the brake chambers
B.When the compressor pumps air into the storage tanks
C.When the spring brakes release
D.How quickly the brake lights come on
Explanation: Section 5.1.2 says the governor controls when the air compressor will pump air into the air storage tanks. It stops the compressor at the cut-out pressure and lets it start again at the cut-in pressure.
5According to Section 5.1.2, at about what pressures does the governor stop and then restart the compressor?
A.Stops at about 100 psi; restarts at about 55 psi
B.Stops at about 150 psi; restarts at about 125 psi
C.Stops at about 125 psi; restarts at about 100 psi
D.Stops at about 90 psi; restarts at about 60 psi
Explanation: Section 5.1.2 says that when tank pressure rises to the cut-out level, around 125 psi, the governor stops the compressor from pumping. When pressure falls to the cut-in level, around 100 psi, the governor lets the compressor start pumping again.
6If the air compressor stops working, why can you still use the brakes for a while?
A.Stored air in the tanks allows several brake applications
B.The spring brakes take over all normal braking until you park
C.The safety valve sends stored air back to the compressor
D.The governor switches the brakes over to a hydraulic backup
Explanation: Section 5.1.3 says the air storage tanks hold enough air to allow the brakes to be used several times, even if the compressor stops working. That reserve is limited, so stop safely and get the problem fixed.
7Compressed air carries contaminants into the storage tanks. What does Section 5.1.4 say collects there, and why does it matter?
A.Fine dirt from the air intake, which wears out the compressor
B.Water and compressor oil, which harm the system; frozen water can cause brake failure
C.Extra alcohol from the evaporator, which softens the brake hoses
D.Rust flakes from the tank walls, which jam the governor
Explanation: According to Section 5.1.4, the air the compressor delivers usually carries some water and some compressor oil, and both are bad for the air brake system. They settle at the bottom of each tank, and in cold weather the water can freeze and make the brakes fail. That is why every tank must be drained completely; with manual drains, that is your job at the end of each driving day.
8Your air tanks have manually operated drain valves. How are they opened, and how often must you drain them?
A.With a special wrench from the mechanic, once each month
B.By a mechanic only, at each annual state inspection
C.By pumping the brake pedal ten times, once each week
D.A quarter turn or a pull cable, at the end of each driving day
Explanation: Section 5.1.4 says manual drain valves are operated 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. Automatic drains expel water and oil on their own and may also allow manual draining.
9Your bus's automatic air tank drains have electric heaters. What are the heaters for?
A.To keep the automatic drain from freezing in cold weather
B.To warm the air before it reaches the brake chambers
C.To dry the brake linings after a heavy rain
D.To speed up the compressor's pressure build-up
Explanation: Section 5.1.4 says automatic air tanks are available with electric heating devices, which help prevent freezing of the automatic drain in cold weather, a real concern in a Maine winter.
10During cold weather, what does Section 5.1.5 say about an alcohol evaporator?
A.It replaces the need to drain the air tanks
B.It should be emptied each night to prevent freezing
C.Check the alcohol container and fill it as needed every day
D.It is used only on vehicles without dual air systems
Explanation: Section 5.1.5 says an alcohol evaporator puts alcohol into the air system to reduce the risk of ice in air brake valves and other parts. Check the alcohol container and fill it as necessary every day during cold weather. Daily tank draining is still needed unless the system has automatic drains.

About the ME CDL Air Brakes Exam

The Maine CDL Air Brakes Knowledge Test is the air brake component of Maine's CDL examination. Under 29-A MRSA §1253(4), failing it or testing in a vehicle without air brakes restricts you from driving air-brake-equipped CMVs. Independent practice by OpenExamPrep covers Section 5 of the Maine CDL Manual, the four-part air brake check in Section 11, and the L and Z restrictions. These multiple-choice questions are a study aid; they do not replace explaining and performing the air brake check in a real vehicle.

Exam sponsor: Maine Department of the Secretary of State, Bureau of Motor Vehicles (BMV). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

A multiple-choice knowledge test, scheduled through the BMV CDL Examination Section with your other CDL knowledge tests. To drive air-braked CMVs without an L restriction, you must also take the skills test in an air-brake-equipped vehicle and correctly explain and perform all four parts of the air brake check during the Vehicle Inspection test.

Time Limit

Not published by Maine BMV

Passing Score

80% on each CDL knowledge test

Exam / Certification Fees

Part of the CDL examination ($70 for Class A, B, or C on the Maine BMV fee table); no separate air brake fee is listed

Exam sponsor website

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

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 Section 5.1 (official weight not published)

Air Brake System Parts

Compressor and governor (cut-in about 100 psi, cut-out about 125 psi), tanks and drains, alcohol evaporator, 150 psi safety valve, S-cam, wedge, and disc brakes, gauges, the low air warning before 55 psi (80 to 85 psi on many large buses), spring brakes at 20 to 45 psi, parking and modulating controls, and ABS.

Manual Section 5.2 (official weight not published)

Dual Air Brake Systems

Primary and secondary systems, building at least 100 psi in both before driving, the warning in either system, and what happens when one half loses pressure.

Manual Section 5.3 (official weight not published)

Inspecting Air Brakes

Compressor belt, slack adjusters (about one inch of movement), automatic adjusters, drums, linings and hoses, and the Step 7 checks: leakage limits, warning signal, spring brakes, the 85 to 100 psi build-up within 45 seconds, and parking and service brakes.

Manual Section 5.4 (official weight not published)

Using Air Brakes

Normal stops, braking with ABS, controlled and stab braking, brake lag (about 32 feet at 55 mph), brake fade, the downgrade technique, low air pressure, and when not to set the parking brakes.

Manual Section 11.1.2 (official weight not published)

Maine Air Brake Check

The four-part air brake check on the Vehicle Inspection test: governor cut-out (120 to 140 psi), applied leakage (3 psi single, 4 psi combination), warning devices before 55 psi, and emergency brake pop-out at 20 to 45 psi.

Manual introduction, 29-A MRSA §1253(4), and 49 CFR 383.95 (official weight not published)

Maine Air Brake Restrictions

The L and Z restrictions, air-over-hydraulic systems, the 80% passing rule, and how to remove an air brake restriction.

Preparing for the ME CDL Air Brakes Exam

What You Need to Know

  • Passing score: 80% on each CDL knowledge test
  • Assessment: A multiple-choice knowledge test, scheduled through the BMV CDL Examination Section with your other CDL knowledge tests. To drive air-braked CMVs without an L restriction, you must also take the skills test in an air-brake-equipped vehicle and correctly explain and perform all four parts of the air brake check during the Vehicle Inspection test.
  • Time limit: Not published by Maine BMV
  • Exam / certification fees: Part of the CDL examination ($70 for Class A, B, or C on the Maine BMV fee table); no separate air brake fee is listed 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

ME CDL Air Brakes: Suggested Study Strategy

1Use the current Maine CDL Manual: the low air warning must come on before pressure drops below 55 psi. Some other study materials say 60 psi, which does not match Maine's manual.
2Keep the leakage limits straight: with the brakes released, under 2 psi a minute for a single vehicle and under 3 psi for a combination; with the foot brake applied, no more than 3 psi for a single vehicle and 4 psi for a combination.
3Practice the downgrade technique: in the proper low gear, brake just hard enough to feel a definite slowdown, release about 5 mph below your safe speed (about three seconds), and repeat.
4Rehearse saying all four parts of the Section 11 air brake check out loud, and learn your test vehicle's manufacturer specifications.

Frequently Asked Questions

How many questions are on the Maine CDL Air Brakes test?

Maine BMV does not publish a question count or time limit for the Air Brakes knowledge test. Federal rules require at least 80% correct on each CDL knowledge test.

Who needs to pass the Maine CDL Air Brakes test?

Anyone who will drive a CMV with air brakes, including air-over-hydraulic brakes. Under 29-A MRSA §1253(4), failing the air brake component or testing in a vehicle without air brakes means the license is restricted from air-brake-equipped CMVs.

What do the L and Z restrictions mean on a Maine CDL?

Maine's code list shows L as No Air Brakes equipped CMV and Z as No Full air brake equipped CMV. Z applies when the skills test is taken in an air-over-hydraulic vehicle; the driver may operate air-over-hydraulic vehicles but not full air brake vehicles.

How do I remove an air brake restriction from my Maine CDL?

The Maine CDL Manual says you must apply and qualify on the air brake knowledge test and qualify on the skills test in an air-brake-equipped vehicle. The driver accompanying you must hold the proper license and endorsements, or the test will be refused.

What are the four parts of Maine's air brake check?

Section 11 of the Maine CDL Manual lists the air gauge and governor cut-out check (about 120 to 140 psi), the air leakage rate test (no more than 3 psi a minute for a single vehicle or 4 psi for a combination with the foot brake applied), the air warning device test (before 55 psi), and the emergency brake test (pop-out between 20 and 45 psi). Missing any part is an automatic failure of the Vehicle Inspection test.

Can I use an interpreter on the Maine CDL Air Brakes test?

No. Maine's CDL Manual says federal regulations prohibit interpreters on CDL knowledge exams, and federal rules require CDL skills tests to be conducted in English. Maine does not publish which languages its CDL knowledge tests are offered in. This practice bank is written in English.