Flashcard Set Preview
Side ASide B
Why must air tanks be drained?
To drain moisture and oil out of the tank
What is a supply pressure gauge used for?
To tell you how much air is in the air tank.
All vehicles with air brakes must have a low air pressure warning signal.
What are spring brakes?
If the airbrakes leak down, springs press the brakes on to stop the vehicle.
Front wheel brakes are good under all conditions.
When you put your brakes on the air brake system works with an electric switch, by air pressure to turn on the brake lights.
What do air brakes use to make the brakes work?
Air brakes are really three different braking systems: service brake, parking brake and emergency brake.
The service brake applies and releases:
The brake when you use the brake pedal during normal driving.
The parking brake applies and releases:
The parking brakes when you use the parking brake control.
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.
The governor controls when the air compressor will pump into the air storage tanks.
The air storage tanks are used to hold compressed air.
When you put on the brakes by pushing down the brake pedal:
Air pressure is applied to the brake pads.
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 S.
What is a dual air brake system?
A two brake system, one operates the front brakes and one operates the back brakes.
What are the slack adjusters?
It is an adjusting nut on the backside of the brake drum used for adjusting the brakes.
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.
How can you test the low pressure warning signal?
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.
What can you check to see if the spring brakes come on automatically?
Step on and off the brake, with the engine off, the parking brake knob should pop out when air pressure falls between 20-40 psi.
What are the maximum leakage rates?
Less than two psi in one minute for single vehicles and less than three psi in one minute for combination vehicles.
Should you ever leave your vehicle unattended without applying parking brakes or chocking the wheels?
If you are away from your vehicle only a short time, you don't need to use the parking brake.
How often should you drain air tanks?
The use of brakes on a long steep downgrade is only a supplement to the braking effect of the engine.
What factors can cause brakes to fade or fail?
A. Not pressing the brake pedal hard enough. B. Over heating, low air pressure, and not relying on the engine braking effect. C. Not taking your foot off the accelerator pedal.
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.
If oil and water collect in the air tanks what can happen to the brakes?
The brakes could fail.
What is the purpose of an alcohol evaporator?
To reduce the risk of ice in the brake valves and other parts in cold weather.
What is another name for controlled braking?