Ontario Z air brake practice test

For Ontario drivers adding the Z (air brake) endorsement and studying The Official Air Brake Handbook. 45 questions on compressor and governor pressures, air tanks and drains, safety and warning devices, foundation brakes, spring brakes, trailer lines and valves, stopping distance, brake fade, ABS, pushrod stroke limits and the daily air brake checks. Your progress is saved on this device.

Our own questions, each answered from The Official Air Brake Handbook published by the Ministry of Transportation on ontario.ca. The handbook does not state the written test’s pass mark, so the exam simulation uses an 80% target.

All 45 questions with answers

For reading through. Tap "Show answer" under a question to see the answer and the reason.

What does the handbook give as the normal pressure range of an air brake system?
1. About 690 to 828 kPa (100 to 120 psi)
2. About 828 to 1000 kPa (120 to 145 psi)
3. About 380 to 552 kPa (55 to 80 psi)
4. About 552 to 690 kPa (80 to 100 psi)
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A. About 690 to 828 kPa (100 to 120 psi) A typical system runs at roughly 690 to 828 kPa (100 to 120 psi). Know the range for your own vehicle and report anything unusual. (MTO Air Brake Handbook: Air Supply Subsystem, air compressor)
Compressor cut-out pressure is normally how much higher than cut-in pressure?
1. 276 to 311 kPa (40 to 45 psi)
2. 35 to 69 kPa (5 to 10 psi)
3. 138 to 173 kPa (20 to 25 psi)
4. 69 to 103 kPa (10 to 15 psi)
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C. 138 to 173 kPa (20 to 25 psi) The gap between cut-in and cut-out is normally 138 to 173 kPa (20 to 25 psi), and that gap sets the normal operating range. (MTO Air Brake Handbook: Air Supply Subsystem, normal pressure range)
Actual compressor cut-out pressure must never be higher than:
1. 1000 kPa (145 psi)
2. 828 kPa (120 psi)
3. 897 kPa (130 psi)
4. 1035 kPa (150 psi)
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A. 1000 kPa (145 psi) Cut-out above 1000 kPa (145 psi) makes the air brake system defective. 1035 kPa (150 psi) is where the safety valve normally opens, not an allowed cut-out. (MTO Air Brake Handbook: Air Supply Subsystem, normal pressure range)
Actual compressor cut-in pressure must never be lower than:
1. 414 kPa (60 psi)
2. 552 kPa (80 psi)
3. 380 kPa (55 psi)
4. 690 kPa (100 psi)
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B. 552 kPa (80 psi) If the compressor only starts pumping again below 552 kPa (80 psi), the system is defective. (MTO Air Brake Handbook: Air Supply Subsystem, normal pressure range)
Which part tells the air compressor when to stop pumping (cut-out) and when to start again (cut-in)?
1. The safety valve
2. The air dryer
3. The one-way check valve
4. The governor
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D. The governor The compressor turns whenever the engine runs, so the governor switches its pumping off at cut-out and back on at cut-in, which also eases the load on the engine. (MTO Air Brake Handbook: Air Supply Subsystem, governor)
Why is the supply tank also called the “wet” tank?
1. It is only used in rain or snow
2. It holds the alcohol for the evaporator
3. It supplies water-based fluid to the brake chambers
4. It collects most of the moisture and oil that drops out of the compressed air
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D. It collects most of the moisture and oil that drops out of the compressed air Compressed air enters the supply tank first, and most of the condensed moisture and compressor oil settles there. (MTO Air Brake Handbook: Air Supply Subsystem, supply or wet tank)
When you drain the air tanks, which one should you drain first?
1. The secondary tank
2. The supply (wet) tank
3. The primary tank
4. Whichever tank shows the lowest pressure
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B. The supply (wet) tank Draining the supply tank first gets rid of its moisture before it can be pushed on into the other tanks. (MTO Air Brake Handbook: Air Supply Subsystem, air-tank drain valve)
What prevents air that has left the supply tank from flowing back into it?
1. One-way check valves
2. The tractor protection valve
3. The governor
4. The safety valve
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A. One-way check valves One-way check valves let air out of the supply tank but not back in. (MTO Air Brake Handbook: Air Supply Subsystem, one-way check valve)
At what pressure does a safety valve normally open?
1. 828 kPa (120 psi)
2. 1035 kPa (150 psi)
3. 1100 kPa (159 psi)
4. 1000 kPa (145 psi)
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B. 1035 kPa (150 psi) Safety valves, usually on the supply tank and air dryer, normally open at 1035 kPa (150 psi) to release excess pressure if the governor fails. (MTO Air Brake Handbook: Air Supply Subsystem, safety valve)
The low air-pressure warning must come on before the pressure in either the primary or secondary tank falls to:
1. 311 kPa (45 psi)
2. 414 kPa (60 psi)
3. 552 kPa (80 psi)
4. 380 kPa (55 psi)
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D. 380 kPa (55 psi) It must activate before 380 kPa (55 psi). Many devices come on at 414 kPa (60 psi) or higher, but 55 psi is the legal minimum. (MTO Air Brake Handbook: Air Supply Subsystem, low air-pressure warning devices)

In an air disc brake, what does the brake chamber pushrod stroke do?
1. Slides a wedge between two brake shoes
2. Turns an S-shaped camshaft that spreads the shoes
3. Pushes brake shoes outward against a drum
4. Presses the brake pads against the rotor
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D. Presses the brake pads against the rotor Disc brakes use a rotor and a caliper holding pads. When the brakes are applied, the pads squeeze both faces of the rotor. Disc brakes have fewer parts than S cam brakes. (MTO Air Brake Handbook: Foundation Brakes, disc brakes)
Where is an air dryer located in the air supply system?
1. Between the primary tank and the front brake chambers
2. On the trailer, next to the gladhands
3. After the dual-service tanks
4. Between the air compressor and the supply tank
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D. Between the air compressor and the supply tank Air from the compressor passes through the dryer, where it cools and passes through a drying material before it reaches the supply tank. (MTO Air Brake Handbook: Air Supply Subsystem, air dryer)
What does an alcohol evaporator do?
1. Lubricates the brake valves
2. Removes oil from the supply tank
3. Adds alcohol vapour to the air so moisture is less likely to freeze
4. Cools the air before it reaches the tanks
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C. Adds alcohol vapour to the air so moisture is less likely to freeze In cold weather even small ice particles can cause brake failure. The alcohol vapour mixes with moisture or ice and reduces freezing. Only products made for this use may go in it. (MTO Air Brake Handbook: Air Supply Subsystem, alcohol evaporator)
Why do most air brake systems split the air into a primary and a secondary circuit?
1. So the trailer gets its own compressor
2. So the spring brakes can be released faster
3. So that if one circuit fails, the other can still stop the vehicle
4. To double the pressure at the wheels
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C. So that if one circuit fails, the other can still stop the vehicle The dual-circuit design is a safety feature: if one circuit fails, the brakes on the wheels served by the other circuit still work. (MTO Air Brake Handbook: Air Supply Subsystem, dual-service tanks; Service Brake Subsystem)
Inside a service brake chamber, what does the compressed air act on to push out the pushrod?
1. A wedge between the shoes
2. A large coil spring
3. A flexible rubber diaphragm
4. A column of brake fluid
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C. A flexible rubber diaphragm Air fills the chamber and moves the diaphragm, which pushes out the pushrod. A return spring brings the pushrod back when the air is released. (MTO Air Brake Handbook: Service Brake Subsystem, air brake chambers)
The effective length of a slack adjuster is the distance between:
1. The two ends of the pushrod
2. The centre of the camshaft and the clevis pin
3. The clamp bolt and the air port
4. The brake chamber and the brake drum
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B. The centre of the camshaft and the clevis pin Fitting the pushrod in the wrong hole changes this length. Slack adjusters on each side of an axle should match so braking is balanced. (MTO Air Brake Handbook: Inspecting Air Brake Components, air brake chambers)
In an “S” cam brake, what forces the brake shoes out against the drum?
1. Hydraulic fluid in the wheel cylinder
2. The S-shaped end of the camshaft as it rotates
3. A wedge pushed between the shoes
4. Pads clamping both sides of a rotor
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B. The S-shaped end of the camshaft as it rotates Pushrod stroke moves the slack adjuster, which turns the camshaft; the S shape on its end spreads the shoes against the drum. It is the most common foundation brake on air-braked vehicles. (MTO Air Brake Handbook: Foundation Brakes, S cam brakes)
Which type of foundation brake has no exposed brake linkage and is designed to adjust itself?
1. “S” cam brake
2. Wedge brake
3. Any drum brake with a manual slack adjuster
4. Disc brake
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B. Wedge brake In a wedge brake, the chamber pushrod slides a wedge between the shoes. There is no exposed linkage and it is designed to be self-adjusting. (MTO Air Brake Handbook: Foundation Brakes, wedge brakes)
How are spring brakes applied?
1. Only by pressing the brake pedal
2. By air filling the spring brake chamber
3. By a large coil spring when air pressure leaves the chamber
4. By the trailer hand valve
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C. By a large coil spring when air pressure leaves the chamber Spring brakes work the opposite way to service brakes: air holds them released, and when the air goes the coil spring applies them. (MTO Air Brake Handbook: Spring Brake Subsystem)
About how much air pressure is normally needed to hold the spring brakes released?
1. 414 kPa (60 psi)
2. 690 kPa (100 psi)
3. 276 kPa (40 psi)
4. 552 kPa (80 psi)
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A. 414 kPa (60 psi) Around 414 kPa (60 psi) cages the spring. Below that, the spring brakes start to apply on their own. (MTO Air Brake Handbook: Spring Brake Subsystem)
The spring (parking and emergency) brake control valve normally has what kind of knob?
1. Round and blue
2. Green and round
3. Red and eight-sided
4. Yellow and four-sided
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D. Yellow and four-sided Yellow, four-sided, push/pull, near the driver. Most are pushed to release the spring brakes and pulled to apply them, but check your vehicle. (MTO Air Brake Handbook: Spring Brake Subsystem, control valves)
The trailer air supply valve normally has what kind of knob?
1. Yellow and four-sided
2. Red and eight-sided
3. Round and blue
4. Black toggle switch
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B. Red and eight-sided Red, eight-sided, push/pull. Push it in to send air to the trailer; pull it out to close it, or when no trailer is attached. (MTO Air Brake Handbook: Trailer Brake Subsystem, trailer air supply valve)
You find a spring brake chamber with a caging bolt sticking out of it. What does this tell you?
1. The brake is out of adjustment but safe to drive
2. It is a long-stroke chamber
3. The spring brake has been disabled and the vehicle should be inspected and repaired right away
4. The chamber is working normally
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C. The spring brake has been disabled and the vehicle should be inspected and repaired right away A caged chamber will not apply the parking and emergency brake. A driver who finds one should have the vehicle inspected and repaired immediately. (MTO Air Brake Handbook: Spring Brake Subsystem, disabling the spring-brake chamber)
When trailer gladhands are colour-coded, which colours go with which line?
1. Red for service, green for supply
2. Red for supply (emergency), blue for service
3. Blue for supply, red for service
4. Yellow for supply, blue for service
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B. Red for supply (emergency), blue for service Red marks the supply or emergency line that fills the trailer tanks; blue marks the service line. Matching the colours helps avoid cross-connecting. (MTO Air Brake Handbook: Trailer Brake Subsystem, connecting a trailer)
What can happen if the trailer supply and service lines are cross-connected?
1. The trailer spring brakes may not release and the service brakes will not work properly
2. The trailer brakes work but a little more slowly
3. Nothing, the lines carry the same air
4. Only the ABS lamp comes on
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A. The trailer spring brakes may not release and the service brakes will not work properly The trailer brakes will not work correctly: the spring brakes may stay on, the towing vehicle may lose air and the service brakes will not function properly. It is not safe to drive. (MTO Air Brake Handbook: Trailer Brake Subsystem, gladhands)

If a trailer breaks away, the trailer supply valve closes by itself when the pressure in the trailer supply line drops to between:
1. 552 and 690 kPa (80 and 100 psi)
2. 138 and 311 kPa (20 and 45 psi)
3. 380 and 414 kPa (55 and 60 psi)
4. 35 and 69 kPa (5 and 10 psi)
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B. 138 and 311 kPa (20 and 45 psi) Between 138 and 311 kPa (20 and 45 psi). Because air rushes out of the supply line, this usually happens well before the dash gauges fall that low. (MTO Air Brake Handbook: Trailer Brake Subsystem, trailer air supply valve)
Trailer spring brakes must apply automatically when the pressure in the trailer supply line drops below:
1. 311 kPa (45 psi)
2. 552 kPa (80 psi)
3. 414 kPa (60 psi)
4. 138 kPa (20 psi)
Show answer
C. 414 kPa (60 psi) Below 414 kPa (60 psi) the trailer spring brakes must come on, for example when the driver pulls the supply valve to park or the supply line breaks. (MTO Air Brake Handbook: Trailer Brake Subsystem, automatic spring brakes)
What must the trailer hand valve never be used for?
1. Applying the trailer brakes while also using the pedal
2. Slowing the trailer on its own
3. Parking or emergency stops
4. Testing the trailer service brakes
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C. Parking or emergency stops The hand valve applies the trailer service brakes through the service line. It is not a parking brake and must not be used for parking or emergency stops. (MTO Air Brake Handbook: Trailer Brake Subsystem, applying trailer service brakes)
What does the tractor protection valve do?
1. Limits braking on the steering axle
2. Removes moisture from the supply tank
3. Keeps the tractor from losing its air if the trailer has an air-loss problem
4. Releases the spring brakes
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C. Keeps the tractor from losing its air if the trailer has an air-loss problem When the trailer supply valve closes, the tractor protection valve closes too, so a trailer problem (or no trailer) does not drain the towing vehicle’s air. (MTO Air Brake Handbook: Trailer Brake Subsystem, tractor protection valve)
What is the danger with a trailer that has spring brake priority?
1. It can be towed before its service brake tanks have enough air to stop it
2. Its hand valve applies the spring brakes
3. Its spring brakes can never be released
4. It cannot be towed until every tank is full
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A. It can be towed before its service brake tanks have enough air to stop it Spring brake priority fills the spring brake tank first, so the trailer can move before its service brakes have enough air. Service brake priority avoids this. (MTO Air Brake Handbook: Trailer Brake Subsystem, spring or service brake priority)
If you double your speed, your stopping distance becomes about:
1. Three times as long
2. The same
3. Four times as long
4. Twice as long
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C. Four times as long Stopping distance grows faster than speed: twice the speed means four times the distance. (MTO Air Brake Handbook: Demands on Brakes While Driving, vehicle speed and weight)
Every air brake system has a short delay between pressing or releasing the pedal and the brakes responding. How long can it be?
1. Up to two seconds
2. There is no delay in a working system
3. Up to one-half second
4. Up to five seconds
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C. Up to one-half second Air has to travel through the system, so a delay of up to half a second is normal and must be allowed for in your following distance. (MTO Air Brake Handbook: Demands on Brakes While Driving; Vehicle Braking Systems)
On a long downhill you find you must press the pedal harder and harder to get the same braking. This is called:
1. Wheel lock
2. Brake lag
3. Brake fade, caused by the brakes overheating
4. Compounding
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C. Brake fade, caused by the brakes overheating As brakes heat up they lose effectiveness. In extreme cases, such as a long hill taken too fast or overloaded, fade can leave you unable to slow or stop. (MTO Air Brake Handbook: Demands on Brakes While Driving, brake fade)
What does an anti-lock braking system (ABS) do?
1. Replaces the spring brakes
2. Reduces brake force to a wheel that is about to lock, to keep steering control
3. Keeps the air tanks from freezing
4. Shortens stopping distance on dry roads
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B. Reduces brake force to a wheel that is about to lock, to keep steering control ABS senses an abnormal drop in wheel speed and eases the brake force to that wheel. It helps prevent skids but you should not expect shorter stopping distances. (MTO Air Brake Handbook: Demands on Brakes While Driving, anti-lock braking systems)
The ABS warning lamp comes on while you are driving. What does the handbook say?
1. Regular braking is still available
2. The trailer brakes are disabled
3. All braking is lost
4. Only the spring brakes still work
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A. Regular braking is still available An ABS malfunction does not take away your normal brakes. (MTO Air Brake Handbook: Demands on Brakes While Driving, anti-lock braking systems)
How often must pushrod stroke (brake adjustment) be checked on a vehicle with air brakes?
1. Only at the annual inspection
2. At least once a day
3. Once a week
4. Every 5,000 km
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B. At least once a day Brakes wear as you drive, and pushrod stroke grows with wear, so adjustment must be checked at least daily. (MTO Air Brake Handbook: Inspecting Air Brake Adjustment)
What is the adjustment limit for a standard (unmarked) size 30 clamp-type brake chamber, the most common size?
1. 2 in (51 mm)
2. 2-1/2 in (64 mm)
3. 1-3/4 in (45 mm)
4. 2-1/4 in (57 mm)
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A. 2 in (51 mm) A standard type 30 chamber is out of adjustment if applied stroke goes past 2 in (51 mm). The 30 LS long-stroke version allows 2-1/2 in (64 mm). (MTO Air Brake Handbook: Brake Adjustment Limits Chart)
What is the most visible and permanent way to recognise a long-stroke brake chamber?
1. Square air line ports (standard chambers have round ports)
2. A trapezoidal tag showing the adjustment limit
3. A longer pushrod yoke
4. A yellow painted clamp
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A. Square air line ports (standard chambers have round ports) Square ports are the surest sign. There is also a trapezoidal tag, but it shows the chamber’s maximum stroke, not its adjustment limit. (MTO Air Brake Handbook: Inspecting Air Brake Adjustment)
To measure applied pushrod stroke, you first bring both air gauges to what pressure, before shutting off the engine and holding the brakes fully applied?
1. 621 to 690 kPa (90 to 100 psi)
2. 380 to 414 kPa (55 to 60 psi)
3. 828 to 1000 kPa (120 to 145 psi)
4. 552 to 587 kPa (80 to 85 psi)
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A. 621 to 690 kPa (90 to 100 psi) Bring both primary and secondary gauges to 621 to 690 kPa (90 to 100 psi), shut the engine off, release the spring brakes and hold the service brakes fully applied. (MTO Air Brake Handbook: Inspecting Air Brake Adjustment, measuring applied pushrod stroke)
To test the low air-pressure warning, you start above 621 kPa (90 psi) with the ignition on and pump the brake pedal. The vehicle fails if the warning:
1. Comes on above 380 kPa (55 psi)
2. Comes on at 414 kPa (60 psi)
3. Does not come on, or only comes on below 380 kPa (55 psi)
4. Goes off at a different pressure than it came on
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C. Does not come on, or only comes on below 380 kPa (55 psi) It passes if it activates at or above 380 kPa (55 psi) on both gauges. The point where it switches off as pressure rises need not match where it came on. (MTO Air Brake Handbook: Inspecting Air Brake System Operation, low air-pressure warning)

In the air pressure build-up test, with the engine at 600 to 900 rpm, pressure must rise from 587 to 690 kPa (85 to 100 psi) within:
1. One minute
2. Two minutes
3. Three minutes
4. 30 seconds
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B. Two minutes More than two minutes means the system is defective. Lower the pressure below 552 kPa (80 psi) first, and close the trailer supply valve if a trailer is attached. (MTO Air Brake Handbook: Inspecting Air Brake System Operation, build-up time)
In the air-loss rate test on a tractor pulling one trailer, what is the most pressure it may lose in one minute with the brakes fully applied?
1. 41 kPa (6 psi)
2. 21 kPa (3 psi)
3. 69 kPa (10 psi)
4. 28 kPa (4 psi)
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D. 28 kPa (4 psi) 28 kPa (4 psi) for a tractor and trailer. A straight truck, tractor or bus may lose 21 kPa (3 psi) and a tractor with two or more trailers 41 kPa (6 psi). Ignore the first drop when the pedal goes down. (MTO Air Brake Handbook: Inspecting Air Brake System Operation, air-loss rates)
How do you test the tractor protection valve?
1. Drain the supply tank and watch the gauges
2. With the trailer supply valve closed and the service line disconnected, apply the service brakes; no air should come out of the service line
3. Pump the pedal until the low-air warning sounds
4. Pull the trailer supply valve and check the trailer spring brakes apply
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B. With the trailer supply valve closed and the service line disconnected, apply the service brakes; no air should come out of the service line If air exhausts from the disconnected trailer service line while you hold the pedal, the tractor protection valve is defective. (MTO Air Brake Handbook: Inspecting Air Brake System Operation, tractor protection valve)
A driver holds an Ontario certificate to adjust brakes with manual slack adjusters. Which is true?
1. They may repair spring brake chambers
2. They may not re-adjust automatic slack adjusters
3. They may also re-adjust automatic slack adjusters
4. They no longer need to check adjustment daily
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B. They may not re-adjust automatic slack adjusters The certificate covers manual slack adjusters only. An automatic slack adjuster that keeps needing re-adjustment is defective and must be repaired by a certified technician. (MTO Air Brake Handbook: Inspecting Air Brake Adjustment, re-adjusting brakes)
Which of these vehicles needs a Z endorsement to drive in Ontario?
1. A car with hydraulic brakes
2. A light truck with hydraulic brakes
3. A medium-duty truck with air-over-hydraulic brakes
4. A school bus with only air parking brakes and hydraulic service brakes
Show answer
C. A medium-duty truck with air-over-hydraulic brakes Air-over-hydraulic brakes require the endorsement. A vehicle whose only air-operated part is the parking brake does not. (MTO Air Brake Handbook: Vehicle Braking Systems, other braking systems)

About the Z endorsement

In Ontario you need a Z endorsement on your licence to drive a vehicle with air brakes. The Official Air Brake Handbook covers how the system works and how to check and adjust it; study it together with the practice questions above. For the Class A or D knowledge test itself, try the Ontario AZ practice test.