The stop light switch: Tells you when the air brake system is low on
air pressure Tells you when you need to use your emergency brakes. Turns on the brake lights when you put on the air brakes.
The application pressure gauge shows how much air pressure you: Have in a modulating control valve Are applying to the brakes * Have in the air tanks.
The spring brakes used on the chambers in a straight truck will bring you to a stop when air pressure drops below psi. 60 100 20.
Some air brake systems have an alcohol evaporator. What may happen if you don't keep the proper level of alcohol? The S-cam may not take back when you
release the brake pedal. Ice may form on the brake drums and wear them out 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? * Reduce your speed and drive to the nearest
garage for repairs. Reduce your speed and test the remaining system while under way. Bring your vehicle to a complete stop right away and safely park. Continue only after the system is tixed.
Why drain water from compressed air tanks? Water can freeze in cold weather and cause brake failure. Water low boiling point reduces braking power. Water cools the compressor too much.
The safety valve is set automatically when pressure is: 50 150 100.
Your truck has a dual air system and one of the systems loses its pressure. What will happen? The manual slack adjusters of the S-cam brakes will not be set properly. Either the front or back brake will not be fully operational. Brake drums will not be fully pressurized.
Parking or emergency brakes of trucks and buses can be legally held on by ______ pressure. air Fluid Spring.
If your truck or bus has dual parking control valves, you can use pressure from a separate tank to: Stay parked twice as long without using up service air pressure. Balance the service brake system when you are parked. 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? 60 45 30.
How should you check that your service brakes are working properly? Park on slight grade, drain off air pressure, set
parking brake and check to the movement. 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. Park on level ground, chock the wheels, engage the parking brakes when you have the correct amount of air pressure to do so and shut the engine off.
.
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. 3 2 1.
During normal driving, spring brakes are usually held back by: Air pressure. Spring pressure. Bolts or clamps.
The air compressor stops pumping air at what psi? 100 125 150.
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.
40 80 60.
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 linings. Proper adjustment of S-cam.
The most common type of foundation brake found on heavy vehicles is the: S-cam drum Wedge drum Disc.
it you must make an emergency stop, you should brake so you: Can keep your vehicle in a straight line. Use the hand brake before the brake pedal. Use the full power of the brakes to lock them.
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? Reduce your speed and test the remaining system while under way. Reduce your speed and drive to the nearest garage for repairs. 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. Check the oil for alcohol content. Change the alcohol from a bottle.
The air loss rate for a straight truck or bus with the engine off and the brakes on should not be more than: 1 psi in 30 seconds. 2 psi in 45 seconds 3 psi in one minute.
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. 50 60 80.
The braking power of the spring brakes: Depenas on the service brakes being in adjustment. Increases when the service brakes are hot. * Is not affected by the condition of the service
brakes.
The air brake lag distance at 55 mph on dry pavement adds about
feet. 12 32 52.
Total stopping distance for air brakes is longer than that for hydraulic brakes due to distance. Brake lag Reaction Effective braking.
It is accepted that too much heat caused by using your brakes too often can also cause: Brake to fade or fail. Brake linings to split up. Modulated control valve to wear out.
Repeatedly partially increasing and pressing the brake pedal may result in: A 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. 1/2 inch 1 inch 1/4 inch.
An air brake system is fully charged at what psi? 125 75 100.
The brake pedal in an air brake system: * Is connected to slack adjusters by a series of
rods and linkages. Controls the speed of the air compressor. Controls the air pressure applied to the brakes.
The S-cam: Forces the brake shoes against the inside of
the brake drum. Controls the air flow to each of the brake chambers. Pulls the brake shoes away from the drum and allow the wheels to roll freely.
Under normal conditions, in order to engage the parking brakes the driver should: Be sure air brakes system is fully pressurized. Turn off the engine. Apply brakes by pulling the parking brake
control knob out.
All air brake equipped vehicles have: An air usage gauge. A supply pressure gauge. A backup hydraulic system.
With air brake vehicles, the parking brake should be used Whenever you leave the vehicle unattended. Only during pre-trip inspections. As little as possible.
If the air compressor should develop a leak, what keeps the air in the tanks? The emergency relay valve. The tractor protection valve. The one-way check valve.
Which of these is NOT a proper time to apply the
parking brakes? o Ii you are going to test the parking brake to
make sure that it holds the vehicle. If you will be stopping for only one hour. 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. To hold your speed when going downhill. As little as possible.
Why should you drain water from compressed
air tanks? Water can freeze in cold weather and cause
brake failure. To keep from fowling the air compressor oil. Water low boiling point reduces braking power.
If the spring brakes are on, when should you push the brake pedal? Never. Only when driving downhill.
Only on a slippery road.
To check the free play of manual slack adjusters of S-cam brakes, you should park on: Level ground and apply the parking brakes,
then apply service brakes. Level ground and drain off air pressure before checking the adjustment. Level ground, chock the wheels and release the parking brakes.
Excessive heat caused by using your brakes too often can also cause: Brake linings to split up. Modulated control valve to wear out. Brake to fade or fail.
It you must make an emergency stop, you should brake so you: Use the hand brake first. Can steer and keep your vehicle in a straight
line. Can steer hard while braking hard.
The use of brakes on a long and steep downgrade under normal conditions is only a supplement to: Use of spring brakes. The use of the front brakes limiting valve. The braking effect of the engine.
The most important thing to do when a low air pressure warning comes on is: Up-shift Downshift. 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: Hydraulic pressure. Spring pressure. Air pressure.
Air braking takes more time than hydraulic braking because: Air brakes take more time to flow through the lines than hydraulic fluid. Air brakes use different brake drums. Air brakes require heavier return springs.
When brakes are applied, the brake shoes will press against the: Slack adjuster. Brake drum or disc. S-cam.
The safety valve discharges automatically at the pressure of: 50 psi 150 psi 100 psi.
Stab braking: Use light steady pressure on the brake pedal. 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. Press hard on brake pedal and apply the hand valve as you stop.
If air pressure is not built up within the correct amount of time, then: You should be ready to use your parking
brakes to stop. Air pressure may drop to a low point while driving, requiring an emergency stop. The alcohol container may be low.
The safety valve reduces pressure at psi. 50 150 100.
What can legally hold a parking or emergency brake in position for a truck, truck tractor, or bus? Spring pressure. Air pressure. Fluid pressure.
The supply pressure gauge shows how much pressure: Is in the air tanks. You have used in this trip. Is going to the brake chamber.
The braking power of the spring brakes: * Can only be tested by highly trained brake
service people. Is not affected by the condition of the service 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 the width of the friction area.
of 1/4 1/2 1/8.
Your brakes are fading when: * The brake pedal feels spongy when you apply
pressure. You have to push harder on a brake pedal to control your speed on a downgrade. Less pressure is needed on the brake pedal for each stop.
If your vehicle has an alcohol evaporator, it is there to: Reduce the risk of icing in air brake valves in cold weather. Boost tank pressure, the same way that turbocharges boost engine Eliminate the need for daily tank draining.
The air compressor governor controls Air pressure applied to the brakes. The speed of the air compressor. When air is pumped into the air tanks.
Modern air brakes combine three different systems. They are the service, the parking, and the
brakes. drum foot 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? Once a week. After every four hours of service. 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. 10 mph 15 mph 5 mhp.
In ideal conditions a truck or bus with air brakes going at 55 mph would require the stopping distance of how many feet? Less than 100 feet More than 300 feet. From 100 to 300 feet.
When is it OK to leave your truck unattended without applying the parking brakes and choking the wheels? If you are only away for a few minutes. If you are conducting a pre-trip inspection Never.
The stop light switch: Tells you when you need to use your
emergency brakes. Turns on the brake lights when you put on the air brakes. Tells you when the air brake system is low on air pressure.
The____ shows how much pressure is in the air tanks supply pressure gauge oil gauge air usage gauge.
To test air service brakes you should:
the service brakes, and then gently pull against the brakes Brake firmly while slowly moving forward. Brake slowly while slowly moving backward.
Stop the vehicle, brake in a low gear, depress.
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. 30 25 35.
If your truck has a dual air brake system, and one of the systems is low on pressure: The brake drums will not be fully operational. The manual slack adjusters on S-Cam brakes
are not set properly. Either the front or rear brakes will not be fully functional.
What happens when your brake drums get very hot? They expand.
They start to smoke They contract.
What is a "Wig Wag" A spring mount for hair pieces. A mechanical arm that signals low air pressure. Part of the stop light system.
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