Ontario AZ Licence Practice Test 2026: Practice test 5

Practice test 5 of 6 for the Ontario AZ Licence Practice Test: 25 more questions with answers and explanations.

Commercial vehicle
Ontario
150 questions
Checked October 10, 2026

Question 1 of 25
Which brake chamber size is the most common?
- Type 30
- Type 12
- Type 36
- Type 6
Show answer
Answer: A. Type 30
The handbook notes that size 30 is the most common chamber.
Question 2 of 25
What do the brake chambers do?
- Remove water and oil from the compressed air
- Turn air pressure into force on the push rod
- Store extra air for the horn and the seats
- Cool the brakes by blowing air on the drums
Show answer
Answer: B. Turn air pressure into force on the push rod
Air enters the chamber and pushes a diaphragm, which moves the push rod.
Question 3 of 25
The low air warning comes on while you are driving. What should you do?
- Stop safely as soon as possible and find the cause
- Close the trailer supply valve and speed up
- Keep driving to the next terminal
- Pump the brake pedal to build pressure
Show answer
Answer: A. Stop safely as soon as possible and find the cause
Low pressure means you are losing braking power and spring brakes may soon apply. Stop safely and find the problem.
Question 4 of 25
During the mechanical inspection, what do you check on the air compressor?
- The tire pressure on the nearest wheel
- The drive belt condition and tension, and the mounting
- The fuel level and the oil in the fuel tank
- The colour of the paint and the make of the compressor
Show answer
Answer: B. The drive belt condition and tension, and the mounting
Check the compressor's belt, pulley, mounting, brackets and fasteners.
Question 5 of 25
An automatic slack adjuster keeps needing to be re-adjusted. What does that mean?
- It is working normally
- The governor is set too high
- There is a defect that must be repaired
- The tires are under-inflated
Show answer
Answer: C. There is a defect that must be repaired
Frequent re-adjustment of an automatic slack adjuster points to a defect in the brake.
Question 6 of 25
What are the service brakes used for?
- Parking overnight only
- Emergency stops only
- Holding the trailer while coupling only
- Normal stopping, applied with the brake pedal
Show answer
Answer: D. Normal stopping, applied with the brake pedal
Service brakes are the brakes you use for normal stops, applied with the pedal.
Question 7 of 25
When is a brake considered out of adjustment?
- When applied push rod stroke is over the limit for that chamber
- When the push rod moves at all during a brake application
- When the drum feels warm after a short drive
- When the brake makes no noise as it applies
Show answer
Answer: A. When applied push rod stroke is over the limit for that chamber
Any push rod stroke over the chamber's adjustment limit means the brake is defective.
Question 8 of 25
Which tests must you pass at DriveTest to get the Z endorsement?
- Only a road test in traffic with air brakes
- Only a vision test and a medical review
- A medical exam and a hearing test
- An air brake knowledge test and a practical test
Show answer
Answer: D. An air brake knowledge test and a practical test
You pass the air brake knowledge test and then book and pass the practical test.
Question 9 of 25
What is the job of the tractor protection valve?
- To keep the tractor's air if the trailer is disconnected or breaks away
- To control the trailer's lights and turn signals
- To measure the trailer's weight before you drive
- To protect the tractor's paint from stones thrown by the trailer
Show answer
Answer: A. To keep the tractor's air if the trailer is disconnected or breaks away
The tractor protection valve prevents air loss from the towing vehicle when no trailer is attached or the trailer lines fail.
Question 10 of 25
What is the adjustment limit for a standard type 24 chamber?
- 35 mm (1-3/8 inches)
- 57 mm (2-1/4 inches)
- 45 mm (1-3/4 inches)
- 64 mm (2-1/2 inches)
Show answer
Answer: C. 45 mm (1-3/4 inches)
A standard type 24 chamber has a 45 mm (1-3/4 inch) limit.
Question 11 of 25
Gladhands connect the air lines between tractor and trailer. Which colour is the supply (emergency) line?
- Red
- Black
- Blue
- Green
Show answer
Answer: A. Red
Red gladhands are for the supply (emergency) line and blue are for the service line.
Question 12 of 25
Which situation is most likely to cause severe brake fade?
- Using the engine brake on a short hill with an empty trailer
- A long downhill run with a heavy load at too high a speed
- Parking overnight in very cold weather with the spring brakes on
- Driving slowly on a flat road in town with many stops
Show answer
Answer: B. A long downhill run with a heavy load at too high a speed
Long descents, overloading and too much speed can overheat the brakes so badly that you cannot stop.
Question 13 of 25
What does the one-way check valve do?
- Stops air from flowing back out of a tank
- Lets air flow both ways freely
- Releases air when pressure is high
- Applies the parking brake
Show answer
Answer: A. Stops air from flowing back out of a tank
A one-way check valve lets air into a tank but prevents it from flowing back out.
Question 14 of 25
Why is the supply tank called the wet tank?
- It collects most of the moisture and oil from the compressed air
- It is mounted under the fuel tank and gets wet in rain
- It is filled with water on purpose to cool the air
- It holds the windshield washer fluid for the cab
Show answer
Answer: A. It collects most of the moisture and oil from the compressed air
The supply tank receives air first and collects most of the moisture and oil.
Question 15 of 25
In the air-loss test, what is the most pressure a tractor and one trailer may lose in one minute?
- 41 kPa (6 psi)
- 14 kPa (2 psi)
- 55 kPa (8 psi)
- 28 kPa (4 psi)
Show answer
Answer: D. 28 kPa (4 psi)
A tractor and trailer may lose no more than 28 kPa (4 psi) per minute.
Question 16 of 25
What is the lowest allowed governor cut-in pressure?
- 414 kPa (60 psi)
- 690 kPa (100 psi)
- 380 kPa (55 psi)
- 552 kPa (80 psi)
Show answer
Answer: D. 552 kPa (80 psi)
The cut-in pressure must not be below 552 kPa (80 psi).
Question 17 of 25
What does it mean if a spring brake chamber is caged?
- It has been filled with oil to stop it from rusting
- It is locked so no one can steal the brake parts
- It has a metal cover to keep out snow and road salt
- Its spring is held back by a caging bolt, so it will not apply
Show answer
Answer: D. Its spring is held back by a caging bolt, so it will not apply
A technician can cage the spring with a bolt, for example to move a vehicle in an emergency. The protruding bolt shows it is caged.
Question 18 of 25
Who may adjust manual slack adjusters?
- Only certified technicians
- Anyone with a wrench
- Any driver with a Z endorsement
- Any passenger
Show answer
Answer: A. Only certified technicians
Only certified technicians may adjust manual slack adjusters. Drivers should not try to repair automatic adjusters.
Question 19 of 25
What is an alcohol evaporator for?
- To add alcohol vapour to the air and reduce freezing in the system
- To test the driver's breath for alcohol before starting
- To cool the engine on long, steep hills
- To clean the windshield in freezing weather
Show answer
Answer: A. To add alcohol vapour to the air and reduce freezing in the system
An alcohol evaporator puts alcohol vapour into the air to help stop moisture freezing in the lines and valves.
Question 20 of 25
What must Z-endorsed drivers aged 80 or older do every year?
- Take a full road test only, with no air brake check
- Retake the full air brake course with a fleet owner
- Nothing extra; renewal is every 5 years as usual
- Complete the online module and an air brake practical test
Show answer
Answer: D. Complete the online module and an air brake practical test
At 80 and older, you must complete the online module and practical test every year.
Question 21 of 25
Why should you never try to take apart a spring brake chamber?
- The spring is under very high tension and can injure you
- Opening it voids the trailer's registration
- It is full of hot oil that can burn your hands
- It contains a sensor that records brake use
Show answer
Answer: A. The spring is under very high tension and can injure you
The spring in the chamber is under very high tension. Never try to service or repair it.
Question 22 of 25
What is a slack adjuster?
- A lever that links the push rod to the brake camshaft
- A spring inside the chamber that holds the parking brake
- A gauge on the dashboard that shows brake wear
- A valve that lets out extra air when pressure is too high
Show answer
Answer: A. A lever that links the push rod to the brake camshaft
The slack adjuster connects the push rod to the camshaft and increases the braking force.
Question 23 of 25
In the air-loss test, what is the most pressure a straight truck, tractor or bus may lose in one minute?
- 21 kPa (3 psi)
- 69 kPa (10 psi)
- 41 kPa (6 psi)
- 7 kPa (1 psi)
Show answer
Answer: A. 21 kPa (3 psi)
A single vehicle may lose no more than 21 kPa (3 psi) per minute.
Question 24 of 25
What does the letter L stamped on a brake chamber cover mean?
- It is a long-stroke chamber, with a longer adjustment limit
- It is a left-side chamber
- It is a low-pressure chamber
- It is a light-duty chamber that is not allowed on trucks
Show answer
Answer: A. It is a long-stroke chamber, with a longer adjustment limit
L marks a long-stroke design. Long-stroke chambers have longer adjustment limits than standard ones.
Question 25 of 25
After your air brake course, you receive a referral envelope. Within how long must you take it to a DriveTest centre?
- 1 year
- 6 months
- 30 days
- 2 years
Show answer
Answer: B. 6 months
Take the referral envelope to a DriveTest centre within 6 months.

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