CDL Air Brakes Practice Test 3 — Questions and Answers
Question 1: What is the proper technique to use when braking on downgrades?
- Use stab braking
- Use controlled braking
- Apply the brakes just hard enough to slowdown about 5 mph below your safe speed (Correct answer)
- Repeatedly pump the brakes to slow the vehicle down
Correct answer: Apply the brakes just hard enough to slowdown about 5 mph below your safe speed
Apply the brakes just hard enough to slowdown about 5 mph below your safe speed. When going down a long/steep downgrade you should use engine braking to slow your vehicle down. After your vehicle is in the proper gear, you can apply the brakes just hard enough to feel a definite slowdown (usually about three seconds). When your speed is about 5 MPH below your safe speed, you can release the brakes.
Question 2: If your vehicle does not have automatic air tank drains, how often should you drain the tanks?
- Once a week
- Every 1,000 miles of travel
- At the end of each working day (Correct answer)
- Twice a week
Correct answer: At the end of each working day
At the end of each working day. Draining the air tanks removes oil and moisture. If you do not drain each working day, you risk brake failure.
Question 3: When is it acceptable to not use parking brakes if you have to leave your vehicle unattended?
- If you are on a flat road surface
- If you will only be gone a short time
- If your wheels are turned at a harsh angle
- You should never leave your vehicle without using parking brakes or chocking the wheels (Correct answer)
Correct answer: You should never leave your vehicle without using parking brakes or chocking the wheels
You should never leave your vehicle without using parking brakes or chocking the wheels. If you leave your vehicle unattended without the parking brakes on or the wheels chocked, the vehicle might roll away.
Question 4: When should parking brakes NOT be used?
- When the brakes are wet in freezing temperatures
- When the brakes are very hot
- When checking that the spring brakes can come on automatically
- All of the above (Correct answer)
Correct answer: All of the above
All of the above. The brakes can freeze if they are applied when wet and the temperature is freezing. The brakes can become damaged if they are applied when they are very hot.
Question 5: Which device is designed to protect the air tank and system from too much pressure?
- Drain valve
- Safety valve (Correct answer)
- Governor
- Evaporator
Correct answer: Safety valve
Safety valve. A safety relief valve is installed in the first tank that the air compressor pumps air into. A safety valve protects the tank and system from too much pressure by opening up at 150 psi. The governor controls when the air compressor will pump air into the air storage tanks. An alcohol evaporator puts alcohol into the air system to help reduce the risk of ice in cold weather.
Question 6: What should you do before driving a vehicle with a dual air system?
- Make sure both primary and secondary system build up to 85 psi
- Make sure that primary system builds up to 125 psi and secondary system builds up to 100 psi
- Make sure that primary system builds up to 100 psi and secondary system builds up to 85 psi
- Make sure that both primary and secondary system build up to 100 psi (Correct answer)
Correct answer: Make sure that both primary and secondary system build up to 100 psi
Make sure that both primary and secondary system build up to 100 psi. Before driving a vehicle with a dual air system, you should allow enough time for the air compressor to build up a minimum of 100 psi on both systems. You should verify this by watching both air pressure gauges.
Question 7: If you press and release the brake pedal rapidly, what will happen?
- You can let the air out faster than the compressor can replace it (Correct answer)
- Your vehicle will stop faster and straighter
- You can safely control your speed around a curve
- You can cool your brakes rapidly
Correct answer: You can let the air out faster than the compressor can replace it
You can let the air out faster than the compressor can replace it. Releasing the brakes lets some compressed air out of the air brake system which results in the reduction of air pressure in the tank. Repeatedly pressing and releasing the brake pedal may reduce the air pressure faster than the compressor can replace it.
Question 8: What is another term for a brake pedal?
- Brake shoe
- Treadle valve (Correct answer)
- S-cam
- Wedge brake
Correct answer: Treadle valve
Treadle valve. A brake pedal can also be known as a treadle valve or a foot valve.
Question 9: What is the name of the device that controls when the air compressor will pump air into the air storage tanks?
- Evaporator
- Governor (Correct answer)
- Safety valve
- Air tank drains
Correct answer: Governor
Governor. The governor controls when the air compressor will pump air into the air storage tanks. An alcohol evaporator puts alcohol into the air system to help reduce the risk of ice in cold weather. A safety valve protects the tank and system from too much pressure. The air tank drains allow you to drain oil and moisture from the air tanks.
Question 10: Which device helps reduce the risk of ice in the air brake systems during cold weather?
- Air compressor governor
- Air tank drain
- Safety valve
- Alcohol evaporator (Correct answer)
Correct answer: Alcohol evaporator
Alcohol evaporator. An alcohol evaporator puts alcohol into the air system to help reduce the risk of ice in cold weather. The governor controls when the air compressor will pump air into the air storage tanks. A safety valve protects the tank and system from too much pressure. The air tank drains allow you to drain oil and moisture from the air tanks.
CDL Air Brakes Practice Test 3
What is the proper technique to use when braking on downgrades?