Air Brakes - Quiz Sample #1, 15 questions
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.
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 lock, put on the brakes again when the wheels start rolling.
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.
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
You should know that your brakes are fading when:
Pressure on the brake pedal is released and speed increases.
You have to apply the brake pedal harder to control speed on a downgrade.
The brake feels spongy when pressure is applied.
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.
To check the brake slack on S-cam brakes you should:
Park on level ground, chock the wheels, and release the parking brake.
Stop on level ground and apply the parking brakes.
Park on level ground and drain off air pressure before adjusting.
The application pressure gauge shows how much pressure you have:
In the tanks.
In a modulating control valve.
When you are applying the brakes.
The spring brakes used in the chambers in a straight truck will bring you to a stop when air pressure drops below ___ PSI.
60
20
100
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 properly.
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.
During normal driving, spring brakes are usually held back by:
Air pressure.
Springs.
Bolts and braces.
The driver must be able to see a warning when air pressure in the service air tanks falls below ___ PSI.
60
50
80
Excessive use of the service brakes results in overheating, which can lead to:
Expansion of the brake drums.
Increase contact between the brake drums and springs
Proper adjustment of S-cam.
The most common type of foundation brakes found on heavy vehicles is the:
Wedge drum.
S-cam drum.
Disc drum.
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.
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.
Total stopping distance for air brakes is longer than that for hydraulic brakes due to ___ distance.
Brake lag
Reaction distance
Effective braking
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.
Repeatedly pressing and releasing (fanning) the brake pedal may result in:
The loss of brake air pressure.
A buildup of brake air pressure.
No change of brake air pressure.
The brake system that applies and releases the brakes when the driver uses the brake pedal is the _____________ brake system.
Emergency.
Service.
Parking.
A slack adjuster’s free play needs to be adjusted if it is more than about ___ when you pull hard on it.
1/4 inch
1/2 inch
1 inch
The brake pedal in an air brake system:
Controls 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.
The S-cam:
Controls the flow of 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.
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 the air brakes system is fully pressurized.
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
When 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.
If the spring brakes are on, when should you push the brake pedal?
Only when driving downhill.
Only on slippery roads.
Never.
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.
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