CDL Air Brake Systems Quiz

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Questions and Answers

What are the three different systems that modern air brake systems combine?

Parking brakes

Service brakes

Emergency brakes

All of the above (correct)

When should you drain the air tanks if you do not have an automatic tank drain?

After every working day.

Why is it important to drain water from the compressed air tanks?

Water can freeze in cold weather and cause brake failure.

What must air brake equipped vehicles have?

A supply pressure gauge. Signup and view all the answers

What can legally hold a parking or emergency brake in position for a truck, truck tractor, or bus?

Spring pressure. Signup and view all the answers

Air loss in a straight truck or bus should not be more than how much with the engine off and the brakes on?

3 psi in one minute. Signup and view all the answers

What should you do to make an emergency stop with air brakes using the stab braking method?

Brake as hard as you can, get off the brakes when the wheels lock, get back on the brakes when the wheels start rolling again. Signup and view all the answers

How do you know your brakes are fading?

You have to push harder on the brake pedal to control your speed on a downgrade. Signup and view all the answers

To check the free play of manual slack adjusters on s-cam brakes, what should you do?

Park on level ground, chock the wheels, and release the parking brakes. Signup and view all the answers

What keeps the air in the tanks if the air compressor develops a leak?

The one way check valve. Signup and view all the answers

When driving down a long steep hill, what should you do?

Release the brake when you are 5 M.P.H. below your safe speed. Signup and view all the answers

What brake system applies and releases the brakes when the driver uses the brake pedal?

Service brake system. Signup and view all the answers

What is the most common type of foundation brakes found on heavy vehicles?

S-cam drum. Signup and view all the answers

What must vehicles with air brakes have?

An air pressure gauge to show the pressure available for braking. Signup and view all the answers

At what pressure level must a driver be able to see a warning before air pressure in the service air tanks falls?

60 psi. Signup and view all the answers

What makes the total stopping distance for air brakes longer than that for hydraulic brakes?

Brake lag distance. Signup and view all the answers

What is the first thing to do when a low air pressure warning comes on?

Stop and safely park as soon as possible. Signup and view all the answers

The braking power of the spring brakes depends on what?

The adjustment of the service brakes. Signup and view all the answers

What does the air compressor governor control?

When air is pumped into the air tanks. Signup and view all the answers

What does the application pressure gauge show the driver?

How much pressure is being applied to the brakes. Signup and view all the answers

If your vehicle has an alcohol evaporator, what should you do every day during cold weather?

Check and fill the alcohol level. Signup and view all the answers

During normal driving, how are spring brakes usually held back?

By air pressure. Signup and view all the answers

Why does air braking take more time than hydraulic braking?

Because air brakes need to have airflow through the lines to work. Signup and view all the answers

When should parking brakes be used in air brake vehicles?

Whenever the vehicle is parked. Signup and view all the answers

What does the brake pedal in an air brake system control?

The air pressure applied to put on the brakes. Signup and view all the answers

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

Release the spring brakes to move a short distance. Signup and view all the answers

A straight truck or bus air brake system should not leak at a rate of more than how much PSI per minute with the engine off and the brakes released?

2 PSI. Signup and view all the answers

What is the purpose of an alcohol evaporator in your vehicle?

To reduce the risk of ice in air brake valves in cold weather. Signup and view all the answers

If you must make an emergency stop, how should you brake?

So that you stay in a straight line and can steer. Signup and view all the answers

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

Stop, safely park, and continue only after the system is fixed. Signup and view all the answers

Study Notes

Air Brake System Overview

Modern air brake systems integrate service brakes, parking brakes, and emergency brakes.
An air pressure gauge is mandatory for vehicles equipped with air brakes to monitor pressure available for braking.

Maintenance and Safety

Drain compressed air tanks after each working day to prevent water condensation, which can freeze and cause brake failure.
If equipped with an alcohol evaporator, check and fill the alcohol level daily during cold weather to minimize ice formation in air brake valves.

Performance Indicators

A loss of no more than 3 psi in one minute is acceptable for straight trucks or buses with the engine off and brakes on.
Parking and emergency brakes should be held in position by spring pressure.

Emergency Procedures

To execute an emergency stop using stab braking, apply brakes hard, release when wheels lock, and reapply when wheels begin to roll again.
The first response to a low air pressure warning is to stop and safely park as soon as possible.

Braking Dynamics

The service brake system activates and releases brakes upon driver input via the brake pedal.
Brake lag distance contributes to longer stopping distances for air brakes compared to hydraulic brakes due to the need for air to flow through lines.

Usage Guidelines

Release brakes when descending a long steep hill when 5 mph below your safe speed.
Parking brakes must be engaged whenever the vehicle is parked, ensuring safety during stops.

Adjustments and Controls

Manual slack adjusters on S-cam brakes require checking free play by parking on level ground, chocking wheels, and releasing parking brakes.
Air compressor governors regulate when air is pumped into the air tanks.

Operational Mechanisms

Spring brakes rely on the proper adjustment of service brakes for effective braking power.
The application pressure gauge indicates how much brake pressure is being applied by the driver.

System Reliability

A one-way check valve is crucial to retain air in the tanks if the air compressor develops a leak.
Vehicles with dual parking control valves can use pressure from a separate tank to release spring brakes for short movements.

Leak Standards

Air brake systems on straight trucks or buses should not exceed a leak rate of 2 psi per minute when the engine is off and brakes are released.
During normal driving, spring brakes remain engaged through air pressure, preventing inadvertent application.

Driving Considerations

Braking power can fade if drastic increases in pedal pressure are required to maintain speed on downgrades.
To maintain control during emergency stops, brake in a manner that keeps the vehicle traveling in a straight line.

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Description

Test your knowledge on modern air brake systems with this quiz. Cover topics such as service, parking, and emergency brakes, as well as maintenance practices like tank drainage. Perfect for CDL students looking to enhance their understanding of air brake operations.