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A. 1 psi in one minute
B. 3 psi in one minute
C. 1 psi in 30 seconds
With a fully-charged air system, turn off the engine, release the parking brake, and time the air pressure drop. The loss rate should be less than two psi in one minute for single vehicle brakes released, and three with the brakes applied.
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A. Air pressure.
B. Electrical.
C. Mechanical force.
Drivers behind you must be warned when you put your brakes on. The air brake system does this with an electric switch that works by air pressure. The switch turns on the brake lights when you put on the air brakes.
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A. 1
B. 2
C. 3
With a fully-charged air system, turn off the engine, release the parking brake, and time the air pressure drop. The loss rate should be less than two psi in one minute for single vehicle brakes released, and three with the brakes applied.
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A. An air pressure gauge to show the pressure available for braking.
B. At least two air tanks.
C. An air pressure gauge to show air used by the brake chambers for braking.
All vehicles with air brakes have a pressure gauge connected to the air tank. If the vehicle has a dual air brake system, there will be a gauge for each half of the system.
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A. 1/2 inch
B. 1-1/2 inches
C. 1 inch
Park on level ground and chock the wheels to prevent the vehicle from moving, release the parking brakes so you can move the slack adjusters, using gloves and pull hard on each slack adjuster that you can reach, and if a slack adjuster moves more than about one inch where the push rod attaches to it then adjustments are needed.
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A. Pump the brakes while your vehicle is fully on.
B. Manually let the air out of your brakes and see if the signal comes on.
C. Pump the brakes until the air pressure drops below 30 psi.
D. With the engine off, step on and off the brake pedal to lower the air pressure below 60 psi.
Shut the engine off when you have enough air pressure so that the low-pressure warning signal is not on. Turn the electrical power on and step on and off the brake pedal to reduce air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 60 psi in the air tank.
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A. None; low air pressure warning signals are optional.
B. All vehicles with air brakes currently in operation must have low air pressure warning signals.
C. Vehicles built after 2010 must have low air pressure warning signals.
D. Vehicles built after 2005 must have low air pressure warning signals.
A low air pressure warning signal is required on vehicles with air brakes.
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A. 5 mph slower.
B. 10 mph slower.
C. 15 mph slower.
Snub braking method is used for steep downhill grades, in this method apply the brakes just hard enough to feel a definite slowdown. When your speed has been reduced to approximately five mph below your "safe" speed, release the brakes. When your speed has increased to your "safe" speed, repeat.
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A. park on level ground, chock the wheels, and release the parking brakes.
B. stop on level ground and apply the parking brakes.
C. park on level ground and drain off the air pressure.
To check slack adjusters on S-cam Brakes. Park on level ground and chock the wheels to prevent the vehicle from moving and apply the parking brake.
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A. so you can coast downhill.
B. so you only have to apply the brake just hard enough to feel a definite slowdown.
C. so you can go through the gears on the way down.
The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine. Once the vehicle is in the proper low gear you should only have to apply the brakes just hard enough to feel a definite slowdown.
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A. turn off the engine.
B. let the air out of the brake chambers.
C. be sure the air brake system is fully pressurized.
A parking brake control in the cab allows the driver to let the air out of the spring brakes. This lets the springs put the brakes on.
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A. between the power screw and push rod on disc brakes.
B. a part of the air brake system that is used to adjust the brakes.
C. all of the above.
D. between the push rod and S-cam on drum brakes.
Slack adjusters are an important part of your air brake system that allows you to adjust the brakes to ensure that they are safe. They are located in different places, depending on the type of brakes that you have.
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A. Emergency brake system
B. Parking brake system
C. Service brake system
D. Radio signal system
Air brakes are really three different braking systems: service brake, parking brake, and emergency brake.
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A. Need to have airflow through the lines to work.
B. Use different brake drums.
C. Require heavier return springs.
With air brakes there is an added delay called Brake Lag. This is the time required for the brakes to work after the brake pedal is pushed.
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A. Whenever the vehicle is parked.
B. To hold your speed when going downhill.
C. Only during pre and post trip inspections.
Any time you park use the parking brakes. Pull the parking brake control knob out to apply the parking brakes, push it in to release.
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A. Controls the speed of the air compressor.
B. Controls the air pressure applied to the brakes.
C. Is to be used as a footrest during normal driving.
You put on the brakes by pushing down the brake pedal. Pushing the pedal down harder applies more air pressure. Letting up on the brake pedal reduces the air pressure and releases the brakes.
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A. Stop, safely park, and continue only when the system is fixed.
B. Reduce your speed and drive to the nearest garage for repairs.
C. Reduce your speed and test the remaining system while underway.
Even if the low-pressure alarm is for the secondary system you need to stop at a safe location, park, and get the issue fixed. It is unsafe for the vehicle to remain in motion with a low air alarm.
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A. will close if you apply the parking brakes.
B. does all of the above.
C. provides the air supply for the brake system.
D. will close automatically if the air supply drops to a certain level.
The tractor protection valve keeps air in the tractor or truck brake system should the trailer break away or develop a bad leak, and it will close automatically if air pressure is low (typically 20-45 psi).
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A. Downshift.
B. Stop.
C. Upshift.
If the low air pressure warning comes on, stop and safely park your vehicle as soon as possible.
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A. Every time you leave your vehicle for any length of time
B. Only if you are away from your vehicle for an extended period of time
C. Every time you leave your vehicle, with a few exceptions
D. Only in urban areas where there are many other vehicles
Never leave your vehicle unattended without applying the parking brakes or chocking the wheels. Your vehicle might roll away and cause injury and damage. Exceptions are when the brakes are very hot, or wet and it is very cold outside. In this case use wheel chocks.
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A. Has been used in this trip.
B. Is in the air tanks.
C. Is being sent to the brake chambers.
All vehicles with air brakes have a pressure gauge connected to the air tank, and it tells you how much pressure is in the air tanks.
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A. Brake drum
B. Return spring
C. Safety valve
D. Slack adjuster
Drum brakes are on each of your vehicle's axles and contain about 10 different parts, including the axle, slack adjuster, and brake drum itself. While a safety valve is part of the air brake system, it is not part of the drum brake.
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A. 120
B. 150
C. 160
A safety relief valve is installed in the first tank the air compressor pumps air to. The safety valve protects the tank and the rest of the system from too much pressure. The valve is usually set to open at 150 psi. If the safety valve releases air, something is wrong. Have the fault fixed by a mechanic.
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A. Use the brakes hard without locking the wheels.
B. Use the stab braking method
C. Use the hand valve and service brakes.
Stab braking means that you: apply your brakes all the way, and release brakes when wheels lock up. As soon as the wheels start rolling, apply the brakes fully again.
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A. They are the CamLaster brakes.
B. If the air brakes leak down, springs apply the brakes to stop the vehicle.
C. They are the springs on the brake pedal.
When driving, powerful springs are held back by air pressure. If the air pressure is removed, the springs put on the brakes. A leak in the air brake system, which causes all the air to be lost, will also cause the springs to put on the brakes.
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