Free CDL Air Brake Pre-Trip Inspection Questions and Answers — Questions and Answers
Question 1: When inspecting the air brake system during a pre-trip, what should you check regarding the air compressor?
- That it turns off and on automatically at specific pressures.
- That it has no visible leaks or damage.
- That it is properly secured and operational.
- All of the above. (Correct answer)
Correct answer: All of the above.
During a pre-trip inspection, it's crucial to thoroughly check the air compressor. This includes verifying that it is securely mounted, free from any visible damage or leaks, and operating correctly. You must confirm that it builds and maintains air pressure within the specified range by turning on and off automatically, ensuring the entire air brake system is functional.
Question 2: How do you check for leaks in the air brake system?
- Listen for hissing sounds while the engine is running.
- Apply full brake pressure, turn off the engine, release the brakes, and watch the pressure gauge. (Correct answer)
- Pump the brakes until air pressure drops below 20 psi.
- Activate the parking brake and check for pressure changes.
Correct answer: Apply full brake pressure, turn off the engine, release the brakes, and watch the pressure gauge.
To properly check for leaks in the air brake system, you should build up full air pressure, then turn off the engine. With the engine off, apply the service brakes fully for one minute and observe the air pressure gauge. A drop of more than 3 psi for single vehicles or 4 psi for combination vehicles indicates a leak that needs to be addressed.
Question 3: What is the proper way to test the low air pressure warning system?
- Press the brake pedal repeatedly until the warning light or buzzer activates. (Correct answer)
- Wait until air pressure drops to zero.
- Turn off the engine and listen for a warning sound.
- Check it only after driving a short distance.
Correct answer: Press the brake pedal repeatedly until the warning light or buzzer activates.
To test the low air pressure warning system, you should turn off the engine (with the key on) and repeatedly press the brake pedal. This action gradually releases air from the tanks. The warning light and/or buzzer should activate before the air pressure drops below 60 psi, indicating that the system is functioning correctly to alert the driver of critically low air pressure.
Question 4: How do you test the parking brake during a pre-trip inspection?
- By applying the parking brake and gently pulling against it in a low gear. (Correct answer)
- By listening for air leaks when the parking brake is engaged.
- By checking the dashboard for warning lights.
- By applying the service brakes and watching the air pressure gauge.
Correct answer: By applying the parking brake and gently pulling against it in a low gear.
To test the parking brake during a pre-trip inspection, you should engage the parking brake, put the vehicle in a low gear (like first gear or drive), and gently attempt to pull forward. The vehicle should resist movement, indicating that the parking brake is holding effectively. This confirms the parking brake's ability to secure the vehicle.
Question 5: How do you perform the air pressure build-up test?
- Ensure the compressor builds pressure from 85 to 100 psi within 45 seconds. (Correct answer)
- Pump the brakes until the pressure drops below 50 psi.
- Observe the air tanks draining water and oil during pressure build-up.
- Accelerate the engine to maximum RPM and check the gauge.
Correct answer: Ensure the compressor builds pressure from 85 to 100 psi within 45 seconds.
The air pressure build-up test verifies the efficiency of the air compressor. With the engine at operating RPM, the compressor should be able to build air pressure from 85 psi to 100 psi within 45 seconds. This test ensures the compressor can quickly replenish air pressure, which is vital for safe and effective braking.
Free CDL Air Brake Pre-Trip Inspection Questions and Answers
When inspecting the air brake system during a pre-trip, what should you check regarding the air compressor?