Air Brakes Flashcards
The application pressure gauge shows how much air pressure you:
Are applying to the brakes
The spring brakes used on the chambers in a straight truck will bring you to a stop when air pressure drops below ___ psi (pound per square inch).
20
Some air brakes have an alcohol evaporator. What may happen if you don’t keep the proper level of alcohol?
Ice may form in the air brake valves and cause brake failure
Your truck or bus has a dual air brake system. If a low-pressure warning comes on for only one system, what should you do?
Bring vehicle to a complete stop immediately and safely park. Continue only after issue is fixed.
Why drain water from compressed air tanks?
Water can freeze in cold weather and cause brake failure.
The safety valve is set automatically when pressure is:
150
Your truck has a dual air system and one of the system loses its pressure. What will happen?
Either the front or back brake will not be fully operational.
Parking or emergency brakes of the trucks and buses can be legally held on by ____ pressure.
Spring
If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:
Release the spring emergency/parking brakes to move a short distance
If your truck has a properly functioning dual air brake system and minimum size air tanks, the air pressure should build up from 85 to 100 psi within how many seconds?
45
How should you check that your service brakes are working properly?
Park on level ground, wait until normal air pressure is reached, release the parking brake and move forward slowly at about 5 mph. Then apply the brakes firmly.
A straight truck or bus air brake system should not leak at the rate of more than __
psi per minute with the engine off and the brakes released.
2
During normal driving, spring brakes are usually held back by:
Air pressure
The air compressor stops pumping air at what psi?
125
The driver must be able to see a low air pressure warning which comes on before pressure in the service air tanks fall below ____ psi.
60
Excessive use of the service brakes results in overheating which can lead to:
Expansion of the brake drums
The most common type of foundation brake found on heavy vehicles is the:
S-cam drum
If you must make an emergency stop, you should brake so you:
Can keep your vehicle in a straight line
Your truck or bus has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do?
Stop right away and safely park. Continue only after the system is fixed
If your vehicle has an alcohol evaporator, every day during cold weather you should:
Check and fill the alcohol level
The air loss rate for a straight truck or bus with the engine off and the brakes on should not be more than:
3 psi in one minute
The braking power of the spring brakes:
Depends on the service brakes being in adjustment
The air brake lag distance at 55 mph on dry pavement adds about ___ feet.
32
Total stopping distance for air brakes is longer than that for hydraulic brakes due to ____ distance.
Brake lag
It is accepted that too much heat caused by using your brakes too often can also cause:
Brake to fade or fail
Repeatedly partially increasing and pressing the brake pedal may result in:
A loss of brake air pressure
The brake system that applies and releases the brakes when the driver uses the brake pedal is the ______ brake system.
Service
A slack adjuster’s free play needs to be adjusted if it is more than about _____ when you pull hard on It.
1 inch
An air brake system is fully charged at what psi?
125
The brake pedal in an air brake system:
Controls the air pressure applied to the brakes
The S-cam:
Forces the brake shoes against the inside of the brake drum
Under normal conditions, in order to engage the parking brakes the driver should:
Apply brakes by pulling the parking brake control knob out
All air brake equipped vehicles have:
A supply pressure gauge
With air brake vehicles, the parking brake should be used:
Whenever you leave the vehicle unattended
If the air compressor should develop a leak, what keeps the air in the tanks?
The one-way check valve
Which of these is NOT a proper time to apply the parking brakes?
• If you will be stopping for only one hour.
• If you are going to test the parking brake to make sure that it holds the vehicle.
• If the brakes are very hot (e.g. Just after coming down a steep grade.
If the brakes are very hot (e.g. Just after coming down a steep grade.
With air brake vehicles, the parking brakes should be used:
Any time when vehicle is parked
If the spring brakes are on, when should you push the brake pedal?
Never
To check the free play of manual slack adjusters of S-cam brakes, you should park on:
Level ground, chock the wheels and release the parking brakes.
Excessive heat caused by using your brakes too often can also cause:
Brake to fade or fail
If you must make an emergency stop, you should brake so you:
Can steer and keep your vehicle in a straight line
The use of brakes on a long and steep downgrade under normal conditions is only a supplement to:
The braking effect of the engine
The most important thing to do when a low air pressure warning comes on is:
Stop and safely park as soon as possible
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 braking takes more time than hydraulic braking because:
Air brakes take more time to flow through the lines than hydraulic fluid.
When brakes are applied, the brake shoes will press against the:
Brake drum or disc
The safety valve discharges automatically at the pressure of:
150 psi
What is the correct way to stab brake?
Apply your brakes all the way. Release the brakes when wheels lock up. As soon as the wheels start rolling, apply the brakes fully again.
If air pressure is not built up within the correct amount of time, then:
Air pressure may drop to a low point while driving, requiring an emergency stop
The safety valve reduces pressure at ___ psi.
150
What can legally hold a parking or emergency brake in position for a truck, truck tractor, or bus?
Spring pressure
The supply pressure gauge shows how much pressure:
Is in the air tanks
The braking power of the spring brakes:
Depends on the brakes being in adjustment
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
Your brakes are fading when:
You have to push harder on a brake pedal to control your speed on a downgrade
If your vehicle has an alcohol evaporator, it is there to:
Reduce the risk of icing in air brake valves in cold weather
The air compressor governor controls:
When air is pumped into the air tanks.
Modern air brakes combine three different systems. They are the service, the parking, and the _________
brakes.
Emergency
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?
At the end of each day of driving
The proper use of the brakes when going down a long steep grade after selecting a proper gear is to brake until your speed is about ___ below the posted speed and release your brake.
5 mph
In ideal conditions a truck or bus with air brakes going at 55 mph would require the stopping distance of how many feet?
More than 300 feet
When is it OK to leave your truck unattended without applying the parking brakes and choking the wheels?
Never
The stop light switch:
Turns on the brake lights when you put on the air brakes
The _____________ shows how much pressure is in the air tanks m.
Supply pressure gauge
To test air service brakes you should:
Brake firmly while slowly moving forward
If you are driving down a steep downgrade and have reached your safe speed of 40 mph, you would apply the service brake until your speed dropped to ___ mph.
35
If your truck has a dual air brake system, and one of the systems is low on pressure:
Either the front or rear brakes will not be fully functional
What happens when your brake drums get very hot?
They expand
What is a “Wig Wag”?
A mechanical arm that signals low air pressure.
