Air Brake Endorsement Test | CDL Tests Online

Question 1 of 103

Oil and water usually collect in compressed air tanks. If you do not have an automatic tank drain, when should you drain the air tanks?

After every working day.
After every four hours of service.
Once a week.

Question 2 of 103

Why drain water from the compressed air tanks?

To keep from fouling the air compressor oil.
Water can freeze in cold weather and cause brake failure.
The low boiling point of water reduces braking power.

Question 3 of 103

The air brake system for a straight truck or bus should not leak at a rate of more than ____ psi per minute with the engine off and the brakes released.

1
2
3

Question 4 of 103

To make an emergency stop with air brakes, using the stab braking method, you should:

Pump the brake pedal rapidly and lightly.
Brake hard until the wheels lock, and then get off the brakes for as much time as the wheels were locked.
Press on the brake pedal as hard as you can, release the brakes when the wheels locked, put on the brakes again when the wheels start rolling.

Question 5 of 103

You should know that your brakes are fading when:

Pressure on the brake pedal is released and speed increases.
You have to the brake pedal harder to control speed on a downgrade.
The brake feels spongy when pressure is applied.

Question 6 of 103

If the air compressor should develop a leak, what keeps the air in the tanks?

The tractor protection valve.
The emergency relay valve.
The one way check valve.

Question 7 of 103

To check the brake slack on S-cam brakes you should park on:

Park on level ground, chock the wheels, and release the parking brakes.
Stop on level ground and apply the parking brakes.
Park on level ground and drain off air pressure before adjusting.

Question 8 of 103

The application pressure gauge shows how much pressure you have:

In the tanks.
In a modulating control valve.
When you are applying to the brakes.

Question 9 of 103

The spring brakes used on the chambers in a straight truck will bring you to a stop when air pressure drops below___ psi.

60
20
100

Question 10 of 103

The safety valve is set to automatically reduce pressure at ____ psi.

150
50
100

Question 11 of 103

Your truck has a dual air system and one of the system loses its pressure. What will happen?

Brake drums will not be fully pressurized.
Either the front or back brake will not be fully operational.
The manual slack adjusters of the S-cam brakes will not be set proper

Question 12 of 103

If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:

Balance the service brake system when you are parked.
Release the spring emergency/parking brakes to move a short distance.
Stay parked twice as long without using up service air pressure.

Question 13 of 103

If your truck has a properly functioning dual air brake system and minimum size air tanks. The air pressure should build from 85 to 100 psi within ___ seconds?

45
60
20

Question 14 of 103

During normal driving, spring brakes are usually held back by:

Air Pressure.
Springs.
Bolts and braces.

Question 15 of 103

The air compressor stops pumping air at at what psi?

125
100
150

Question 16 of 103

The driver must be able to see a warning before pressure in the service air tanks falls below _____ psi.

55
50
80

Question 17 of 103

Excessive use of the service brakes results in overheating which can lead to:

Expansion of the brake drums.
Expansion of the brake drums.
Proper adjustment of S-cam.

Question 18 of 103

The most common type of foundation brake found on heavy vehicles is the:

Wedge drum.
S-cam drum.
Disc drum.

Question 19 of 103

If you must make an emergency stop, brake so you:

Use the hand brake before the brake pedal.
Can steer and your vehicle stays in a straight line.
Use the full power of the brakes to lock them.

Question 20 of 103

The braking power of the spring brakes:

Is not affected by the condition of the service brakes.
Increases when the service brakes are hot.
Depends on the service brakes being in adjustment.

Question 21 of 103

The air brake lag distance at 55 mph on dry pavement adds about ____ feet.

32 feet.
45 feet.
65 feet.

Question 22 of 103

Total stopping distance for air brakes is longer than that for hydraulic brakes due to ______ distance.

Brake lag.
Reaction distance.
Effective braking.

Question 23 of 103

It is accepted that too much heat caused by using your brakes too often can also cause:

Modulated control valve to wear out.
Brake linings to split up.
Brake fade or failure.

Question 24 of 103

Repeatedly pressing and releasing (fanning) the brake pedal may result in:

The loss of brake air pressure.
A build up of brake air pressure.
No change of brake air pressure.

Question 25 of 103

The brake system that applies and releases the brakes when the driver uses the brake pedal is the __________ brake system.

Emergency.
Service.
Parking.

Question 26 of 103

A slack adjuster’s free play needs to be adjusted if it is more than about ____ how many inches when you pull hard on it?

1/4 inch
1/2 inch
1 inch

Question 27 of 103

An air brake system is fully charged at what psi?

125
150
75

Question 28 of 103

The brake pedal in an air brake system:

Control the speed of the air compressor.
Controls the air pressure applied to put on the brakes.
Is connected to slack adjusters by a series of rods and linkages.

Question 29 of 103

The S-cam:

Controls the flow air to each of the brake chambers.
Pulls the brake shoes away from the drum and allow the wheels to roll freely.
Forces the brake shoes against the inside of the brake drum.

Question 30 of 103

Under normal conditions in order to engage the parking brakes the driver must first:

Turn off the engine
Let the air out of the spring brakes.
Be sure air brakes system is fully pressurized.

Question 31 of 103

Which of these is NOT a proper time to apply the parking brakes?

If your brakes are very hot.
To use parking brakes if you park for less than 1 hour.
If you are going to use the parking brakes you need to make sure that they will hold the vehicle.

Question 32 of 103

If the spring brakes are on, when should you push the brake pedal?

Only when driving downhill.
Only on the slippery road.
Never.

Question 33 of 103

What is the first thing you should do when a low air pressure warning comes on:

Upshift.
Downshift.
Stop and safely park as soon as possible.

Question 34 of 103

The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like:

Spring pressure.
Air pressure.
Hydraulic pressure.

Question 35 of 103

Air braking takes more time than hydraulic braking because air:

Takes more time to flow through the lines than hydraulic fluid.
Air brakes use different brake drums.
Brakes require heavier return springs.

Question 36 of 103

When you apply the brakes, the brake shoes/linings are pressed against the:

Brake drum.
Slack adjuster.
S-cam.

Question 37 of 103

If air pressure is NOT build up fast enough within the correct amount of time:

You should be ready to use your parking brakes to stop.
The alcohol container may be low.
You air pressure may drop too low during driving.

Question 38 of 103

The proper method of braking when going down a long and/or steep grades after selecting the proper gear, is to brake until your speed is about ___ miles per hour below your “safe” speed, then release your brakes.

5
15
10

Question 39 of 103

In ideal conditions a truck or bus with an air brake going at 55 mph would require stopping distance of how many feet?

From 100 to 250 feet.
Less than 100 feet.
More than 300 feet.

Question 40 of 103

It is not safe to drive a vehicle that has brake drums with cracks that are longer than _____ of the width of the friction area.

1/2
1/4
1/32

Question 41 of 103

Why must air tanks be drained?

To drain all the air out of the tank.
To drain moisture and oil out of tank.
To tell you how much air is in the air tanks.

Question 42 of 103

It is possible to have an air leak in one system which will not affect the other.

True
False

Question 43 of 103

Both systems run off of the same air compressor, so if one air compressor malfunctions you will not be able to build or maintain pressure in either system.

True
False

Question 44 of 103

All vehicles with air brakes must have a low pressure warning signal.

True
False

Question 45 of 103

What are spring brakes?

Brakes used for parking.
If the air brakes leak down, springs press the brakes on to stop the vehicle.
The spring on the brake pedal.

Question 46 of 103

Front wheel brakes are good under all conditions.

True
False

Question 47 of 103

When you apply your brakes, the air brake system works with an electric switch, by air pressure, to turn on the brake lights.

True
False

Question 48 of 103

What do air brakes use to make the brakes work?

Compressed gas.
Compressed oil.
Compressed air.

Question 49 of 103

The service brake applies and releases:

The parking brake when you use the parking brake control.
The brake when you use the brake pedal during normal driving.
In the event of an emergency.

Question 50 of 103

The parking brake applies and releases:

The brake pedal during normal driving.
In the event of an emergency.
The parking brakes when you use the parking brake control.

Question 51 of 103

The emergency brake system:

Uses parts of the service and parking brake system to stop the vehicle in the event of a brake system failure.
Uses the service brake to stop the vehicle in the event of a brake system failure.
Uses the parking brake to stop the vehicle in the event of a brake system failure.

Question 52 of 103

The governor controls when the air compressor will pump into the air storage tanks.

True
False

Question 53 of 103

When the air pressure falls to the minimum pressure allowed in the system, the governor prevents more air from escaping the air tanks.

True
False

Question 54 of 103

The storage tanks are used to hold compressed air.

True
False

Question 55 of 103

When you put the brakes on by pushing down on the brake pedal:

The air pressure is reduced to the brake pads.
Air pressure is applied to the brake pads.
Compressed air is let go out of the system.

Question 56 of 103

The S-cam forces the brake shoes away from one another and presses them against the inside of the brake drum. It is called the S-cam because:

It is shaped like the letter "Z".
It is shaped like the letter "N".
It is shaped like the letter "S".

Question 57 of 103

What is a dual air brake system?

A two brake system, one operates the front brakes and one operates the back brakes.
A two braking system, one for each side of the vehicle.
A two braking system, one for daytime and one for nighttime driving.

Question 58 of 103

What are the slack adjusters?

It is the space between the back wheels.
It is an adjusting nut on the the backside of the brake drum used for adjusting the brakes.
It is an adjusting nut under the cab to adjust the springs.

Question 59 of 103

How can you check the slack adjuster?

Park on level ground, turn off parking brakes, pull hard on each slack adjuster. It shouldn't move more than one inch.
Park on level ground, turn off parking brakes and press brake pedal.
Park on an incline and see if the vehicle rolls.

Question 60 of 103

How can you test the low pressure warning signal?

While the engine is running, step on and off the brake pedal.
Shut off the engine and see if the air pressure leaks down.
Shut off the engine with enough air pressure, turn on the electrical power and step on and off the brake pedal until the low air pressure warning signal comes on.

Question 61 of 103

What are the maximum leakage rates?

Less than 4 psi in one minute for single vehicles and less than 8 psi in one minute for combination vehicles.
Less than 2 psi in one minute for single vehicles and less than 3 psi in one minute for combination vehicles.
Less than 6 psi for all vehicles.

Question 62 of 103

When is it OK to leave your truck unattended without applying
parking brakes or chocking the wheels?

If you will only be away from the truck for a few minutes.
Never.
If you are conducting your pre-trip inspection.

Question 63 of 103

If you are away from your vehicle for only a short time you don’t need to use the parking brake.

True
False

Question 64 of 103

If you do not have automatic tank drains, how often should you drain the oil and water from the bottom of compressed air storage tanks?

After every four hours of service.
At the end of each day of driving.
Once a week.

Question 65 of 103

The use of brakes on a long steep downgrade is only a supplement to the braking effect of the engine.

True
False

Question 66 of 103

What factors can cause brakes to fade or fail?

Not pressing the brake pedal hard enough.
Over heating, low air pressure, and not relying on the engine braking effect.
Not taking your foot off the accelerator.

Question 67 of 103

Why should you be in the proper gear before starting down a hill?

So you only have to apply the brake just hard enough to feel a definite slowdown.
So you can coast downhill.
So you can go through the gears on the way down.

Question 68 of 103

If oil and water collects in the air tanks what can happen to the brakes?

The brakes could heat up.
The brakes could fail.
The brakes could lock up.

Question 69 of 103

What is the purpose of an alcohol evaporator?

So you don't have to drain the air tanks as often.
To have a drink available if you get thirsty.
To reduce the risk of ice in the brake valves and other parts in cold weather.

Question 70 of 103

What is another name for controlled braking?

Steady braking.
Squeeze braking.
Hard braking.

Question 71 of 103

The brake chamber fills with air pushing the rod out which moves the _______ ________, which twists the _____________.

Brake camshaft and tie rod.
Slack adjuster and tie rod.
Slack adjuster and brake camshaft.

Question 72 of 103

If your vehicle has an alcohol evaporator you should check and fill the alcohol level everyday during cold weather.

True
False

Question 73 of 103

To test the air service brakes you should:

Stop the vehicle, put it in low gear, depress the service brake, and then gently pull against the brakes
Brake firmly while slowly moving backwards.
Brake firmly while slowly moving forward.

Question 74 of 103

The driver must be able to see a low pressure warning which comes on before pressure in the service air tank falls below:

60 psi
80 psi
100 psi

Question 75 of 103

Converter dollies built on or after March 1, 1998 are required to have anti lock brakes. These dollies will have:

A yellow malfunction lamp in the center of the dolly.
A yellow malfunction lamp on the right side of the dolly.
A yellow malfunction lamp on the left side of the dolly.

Question 76 of 103

Which of these is the most important thing to remember about emergency braking?

Disconnecting the steering axle brakes will help keep your vehicle in a straight line during emergency braking
Never do it without downshifting first.
If the wheels are skidding, you cannot control the vehicle.

Question 77 of 103

Controlled braking:

Involves locking the wheels for short periods of time.
Can be used while you are turning sharply.
Is used to keep a vehicle in a straight line when braking.

Question 78 of 103

To correct a drive-wheel braking skid, you should:

Increase braking.
Stop braking, turn quickly, and countersteer.
Increase braking, turn quickly, and countersteer.

Question 79 of 103

How do you test the hydraulic brakes for leaks?

Drive slowly and pump the brake pedal. Make sure it doesn't hit the floor.
Pump the brake pedal three times, then apply firm pressure to the pedal and hold for five seconds. The pedal should not move.
Drive 20 mph and slam on the brakes.

Question 80 of 103

Modern air brake systems are three different systems combined together. They are the service, parking, and the _____ brakes.

Emergency.
Foot.
S-cam.

Question 81 of 103

The air supply pressure gauge shows how much pressure:

Is in the air tanks.
You have used in this trip.
Is going to the brake chambers.

Question 82 of 103

The parking or emergency brakes of trucks or buses can legally be held on by ____ pressure.

Spring.
Fluid.
Air.

Question 83 of 103

Air brake equipped vehicles have:

An air use gauge.
An air supply pressure gauge.
A backup hydraulic system.

Question 84 of 103

The stop light switch:

Turns on the brake lights to warn drivers behind you.
Tells you when you need to use your emergency brakes.
Tells you when the air brake system is low on air pressure.

Question 85 of 103

The air loss rate for a straight truck or bus with the engine off and the brakes on should not be more than:

1 psi in one minute.
2 psi in 45 seconds.
3 psi in one minute.

Question 86 of 103

With air brake vehicles, the parking brakes should be used:

Whenever you leave the vehicle unattended.
As little as possible.
Only during pre-trip and post-trip inspections.

Question 87 of 103

The use of air brakes on a downgrade is only a supplement to the:

Use of the spring brakes.
Use of the front brake limiting valve.
Braking effect of the engine.

Question 88 of 103

Excessive heat in the brakes can cause the:

Modulating control valve to wear out.
Brake lines to plug.
Brakes to fade or fail.

Question 89 of 103

You are on a steep down grade and have reached your safe speed of 40 mph. You would apply the service brakes until your speed drops to ___ mph.

25
35
30

Question 90 of 103

If your bus or truck has dual parking control valves, you can use pressure from a separate tank to:

Balance the service brake system when you are parked.
Stay parked twice as long without using up service air pressure.
Release the spring emergency/parking brakes to move a short distance.

Question 91 of 103

The modulating control valve allows you to control the:

Spring brakes.
Front brakes.
Amount of pressure in the brake system.

Question 92 of 103

Some air brake systems have an alcohol evaporator. What may happen if you don’t keep the unit filled with alcohol?

The S-cam may not rotate back when you release the brake pedal.
Ice may form in the air storage tanks and cause the brakes to fail.
Ice may form on the brake pads and warp them.

Question 93 of 103

Before driving a truck or bus with a dual air brake system, the pressure in each air brake system should be at least ___ psi.

80
100
120

Question 94 of 103

How should you check that the spring brakes come on when the air pressure in the system drops below a certain level?

Park on a slight incline, drain off air pressure, set parking brakes and check for movement.
Park on level ground, chock the wheels, release the parking brake when you have enough air pressure, shut the engine off, and repeatedly press and release the brake pedal.
Park on level ground, wait for normal air pressure, release the parking brake, move the truck forward slowly, and apply the brakes firmly using the brake pedal.

Question 95 of 103

For air brake systems in good condition, the air compressor should start pumping at about __ psi.

100
125
150

Question 96 of 103

In air brake vehicles, the parking brake should be used:

As little as possible.
Any time the vehicle is parked.
To hold your speed when going down hill.

Question 97 of 103

The air compressor governor controls:

When air is pumped into the air storage tanks.
The speed of the air compressor.
Air pressure applied to the brakes.

Question 98 of 103

The most important thing to do when a low air pressure warning comes on is:

Upshift.
Downshift.
Stop and safely park as soon as possible.

Question 99 of 103

If your vehicle has an alcohol evaporator, everyday during cold weather you should:

Check and fill the alcohol level.
Change the alcohol from a new bottle.
Check the oil for alcohol content.

Question 100 of 103

Your bus or truck has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do?

Reduce your speed and drive to the nearest garage for repairs.
Reduce your speed and test the remaining system while driving.
Stop and safely park. Continue only after the system is fixed.

Question 101 of 103

It is not safe to drive a vehicle that has brake drums (or discs) with cracks or that are thinner than the manufacturer’s specifications, generally this will be ___ an inch.

1/3
1/4
1/2

Question 102 of 103

Emergency controlled braking is when you:

Apply the brakes as hard as you can without locking the wheels.
Brake as hard as you can, release the brakes when the wheels lock, and put the brakes back on again when the wheels start rolling.
Apply the hand valve for one second, then push hard on the brake pedal.

Question 103 of 103

When performing your air brake leak down test your engine should be turned off.

True
False

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