Air brake systems are three braking systems combined. What are these braking systems?
The air compressor is an important part of the air brake system. What is the purpose of the air compressor?
The emergency brake system uses parts of what brake systems to stop the vehicle in case of a brake system failure?
The cut-out level and cut-in level for the air compressor governor are roughly what pressure per square inch (PSI)?
Compressed air usually contains what substances that are harmful to the brake system?
For a manual air tank, the water and oil are expelled by _____.
Some air brake systems have an alcohol evaporator. What is the purpose of the alcohol evaporator?
What device protects the tank and the rest of the air brake system from too much pressure?
How does letting up on the brake pedal release the brakes?
What can be caused by the unnecessary pressing and releasing of the brake pedal?
When you push the brake pedal down, what force or forces push back against your foot?
What is the most common type of foundation brakes?
When the brakes are applied, brake shoes and linings are pushed against what?
What are forced away from each other and against the inside of the brake drum by the S-cam?
Wedge brakes have a chamber push rod. What does the push rod do?
How do disc brakes primarily differ from S-cam brakes?
Which air braking system is the most common?
What does the supply pressure gauge indicate?
If application pressure must be increased to maintain a certain speed while going down a steep grade, then this most likely means what?
A low air pressure warning comes on before what PSI?
What does the front brake limiting valve in some older vehicles do when turned to “slippery”?
Why are front brake limiting valves not present in newer trucks?
What does it mean when the “wig wag” drops a mechanical arm into your view?
What can a leak in the air brake system cause?
When the parking brake is engaged, what does it do to the spring brakes?
What should be done when the spring brake low air pressure buzzer and warning light first come on?
Some vehicles have a modulating control valve. What does a modulating control valve do?
What controls the parking brakes in newer vehicles?
What should you never do when the spring brakes are on?
Some vehicles, such as buses, have a separate air tank used to do what?
Most heavy-duty vehicles nowadays have a dual air brake system. What is a dual air brake system?
In a dual air brake system, which parts of braking does each system typically operate?
Before driving a vehicle with a dual air system, the driver must allow what to happen?
Checking the air compressor drive belt should be done during what step of the basic seven-step inspection procedure?
Checking the manual slack adjusters on the S-cam brakes should be done during what step of the basic, seven-step inspection procedure?
Which of these should not be done during the final step of the basic, seven-step inspection procedure?
Chocking the wheels, releasing the parking brake when there is enough pressure to do so, shutting the engine off, and then stepping on and off the brake pedal will test what?
With the engine at operating RPM, air tank pressure in a dual system should build from 85 PSI to 100 PSI within how much time?
To test the air leakage rate, one must turn off the engine (with a fully charged air system), turn the key to the “on” position, release the service brake, and do what?
When testing the air leakage rate, the initial loss rate should be less than what PSI/minute for single vehicles and what PSI/minute for combination vehicles?
The loss rate for single vehicles should be less than 2 PSI and the loss rate for combination vehicles should less than 3 PSI in 1 minute. After applying 90 PSI or more with the brake pedal, if the loss rate exceeds 3 PSI for single vehicles and 4 PSI for combination vehicles, the vehicle should be inspected for air leaks.
Applying the brakes as hard as you can without locking the wheels is called what?
Pressing on the brakes as hard as you can, releasing when they lock up, then pressing the brakes fully again when the wheels are rolling is called what?
With air brakes, there is an added delay when stopping. What causes this?
The total stopping distance for vehicles with air brake systems is made up of four factors. Which of the following is not one of these factors?
What is the correct way to slow a large vehicle down on long downgrades?
Brakes can heat up if used excessively. When they become too hot, such as when used on long downgrades, they will fade. They can fade to the point where they will not slow the vehicle down. Shifting into a lower gear and driving at a slow enough speed that a small amount of braking will keep you from speeding up is the best method of avoiding this.
Why is it especially important to have your brakes adjusted before going down steep grades?
Chemical changes in the brake lining, which reduce friction and cause expansion of the brake drums, is known as what?
If your “safe” speed is 45 miles per hour and you are traveling at 60 miles per hour on a downgrade, you should apply the brakes until you have slowed to what speed?
If your “safe” speed is 45 miles per hour, you should not apply the brakes until you have reached what speed?
In what instances should you not use the parking brakes when parking?
If parking brakes are not being used when the vehicle is parked, what must be done instead?