CDL Air Brakes Test
Terms in this set (81)
To test air service brakes you should:
Brake firmly while slowly moving forward
The driver must be able to see a low air pressure warning which comes on before pressure in the service air tanks falls below ____ psi
If your vehicle has an alcohol evaporator, every day during cold weather you should:
Check and fill the alcohol level
All air brakes equipped vehicles have:
A supply pressure gauge
The most common type of foundation brake found on heavy vehicles is the:
Modern air brakes combine three different systems. They are the service, the parking, and the ___ brakes.
To check the free play of manual slack adjusters of s-cam brakes, you should park on:
Level ground, chock the wheels and release parking breaks
Why should you drain water from compressed air tanks?
Water can freeze in cold weather and cause brake failure
The spring brakes used on the chambers in a straight truck will bring you to a stop when air pressure drops below____ psi
With air brake vehicles, the parking brake should be used:
Whenever you leave the vehicle unattended
The safety valve is set automatically when pressure is
Repeatedly partially increasing and pressing the brake pedal may result in:
A loss of air brake pressure
If your truck has dual air brake system, and one of the systems loses its pressure, what will happen?
Either the front or rear brakes will not be fully functional
If you must make an emergency stop, you should brake so you:
Can steer and so your vehicle stays in a straight line
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
You brakes are fading when:
You have to push harder on a brake pedal to control your speed on a downgrade
Which one of these is NOT a proper time to apply the parking brakes?
If the brakes are very hot
The braking power of the spring brakes:
Depends on the service brakes being in adjustment
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 your vehicle to a complete stop right away and safely park. Continue only after the system is fixed
A slack adjusters free play needs to be adjusted if it is more than about _____ when you pull hard on it.
The air brake lag distance at 55 mph on dry pavement adds about _____ feet
An air brake system is fully charge at what psi?
Emergency stab braking is:
Press on the brake pedal as hard as you can, release the brakes when the wheels lock, put on the brakes again when the wheels start rolling
The safety valve discharges automatically at the pressure of:
The air compressor stops pumping air at what psi?
If air pressure is not built up within the correct amount of time, then:
Air pressure may drop to low point while driving, requiring an emergency stop
Parking or emergency brakes of trucks and buses can be legally held on by _____ pressure
If air is not built up within the correct amount of time, then:
Air pressure may drop to a point while driving, requiring an emergency stop
The air compressor governor controls:
When air is pumped into the air tanks
Excessive use of the service brake results in overheating which can lead to:
Expansion of the brake drums
When is it OK to leave your truck unattended without applying the parking brakes and choking the wheels?
The use of brakes on a long and steep downgrade under normal conditions is only a supplement to:
the breaking effect of the engine
The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like:
Is it accepted that too much heat caused by using your brakes too often can also cause:
Brake to fade or fail
The most important thing to do when a low air pressure warning comes on is:
Stop and safely park as soon as possible
With air brake vehicles, the park brakes should be used:
Any time when vehicle is parked
If the spring brakes are on, when should you push on the brake pedal?
The brake system that applies and releases the brakes when the driver uses the brake pedal is the ______ brake system.
An air brake system is fully charged at what psi?
If you are driving down to the steep downgrade and you have reached the speed of 40 mph, you would apply the service brake until your speed dropped to below ___ mph.
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.
What is a "wig wag"?
A mechanical arm that signals low air pressure
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
The application pressure gauge shows how much air pressure you:
Are applying to the brakes
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
Some air brakes systems have an alcohol evaporator. What may happen if you don't keep the proper level of alcohol?
Ice may form in the air storage tank and cause a break failure
Under normal conditions, in order to engage the parking brakes, the driver should:
Let the air out of the brake system
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 5mph, then apply the brakes firmly.
Why drain water from compressed air tanks?
Water can freeze in cold weather and cause brake failure
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?
During normal driving, spring brakes are usually held back by:
The most common type of of foundation brake found on heavy vehicles is the:
Your truck 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
Total stopping distance for air brakes is longer than that for hydraulic brakes due to ______ distance
The brake pedal in the air brake system:
Controls the air pressure applied to put on the brakes
Forces the brake shoes against the inside of the brake drum
If the air compressor should develop a leak, what keeps the air in the tanks?
The one way check valve
Excessive heat caused by using your brakes too often can also cause:
Brake to fade or fail
Air braking takes more time than hydraulic braking because air:
takes 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 reduces pressure at ___ psi.
What can legally hold a parking or emergency brake in position for a truck, truck tractor, or bus?
The supply pressure gauge shows how much pressure:
is in the tanks
If your vehicle has an alcohol evaporator, it is there to:
Reduce the risk of icing in air brake valves in cold weather
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 ___ mph below the posted speed for your safety and release your brake.
In ideal conditions a truck or bus with an air brake going at 55 mph would require stopping distance if how many feet?
more than 300 feet
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.
Supply pressure gauge
What happens when your brake drums get very hot?
If air pressure does NOT build up to normal withing the correct amount of time, then:
Your air pressure may drop too low during driving, requiring an emergency stop
Which of these is NOT a proper time to apply the parking brake?
If the brakes are very hot (example after just coming down a steep grade)
For air brake systems in good condition, the air compressor should start pumping at about ____ psi.
"Cut-out" pressure is normally set to _____ psi.
In newer vehicles, parking brakes are applied using:
A yellow diamond shaped push-knob
Front brake limiting valves are found on:
older vehicle made before 1975
What color is the parking control knob on the dash of the vehicle?
"Cut-in" pressure is normally set to ___ psi.
Which of the following is not an air brake subsystem?
Spring brake system
The safety relief valve has opened several times. This means _____.
The system needs immediate attention
To test the air compressor on a dual air brake vehicle, run the engine at a fast idle to charge the air system. You gauges should show your ______.
Your pressure build from 85 psi within 45 seconds