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CDL Air Brakes Test practice questions

252 free questions with answers and explanations.

Practice test
  1. 51.A driver observes that the air pressure gauge for the primary air tank is consistently reading 10-15 psi lower than the secondary air tank gauge, even after the compressor has built full pressure. Both gauges appear to be working. What is the most likely cause?Air Brake System Parts
  2. 52.A driver notices that when they release the parking brake control knob, the spring brakes on the vehicle do not fully release, causing the vehicle to drag. What is the most likely cause of this issue?Air Brake System Parts
  3. 53.A driver is performing a pre-trip inspection. After turning on the engine, they notice the Anti-lock Braking System (ABS) indicator light illuminates briefly and then turns off. What does this behavior indicate?Air Brake System Parts
  4. 54.A driver is performing a brake test on a vehicle equipped with dual air brake systems. After fully charging the system, the driver applies the parking brake and then releases the service brake. Which of the following should occur?Air Brake System Parts
  5. 55.A technician is diagnosing an issue where a commercial vehicle's spring brakes are not releasing properly, even with adequate air pressure in the system. Which component is the most likely culprit?Air Brake System Parts
  6. 56.A driver is performing a pre-trip inspection and notices that the air pressure in the system consistently builds from 85 psi to 125 psi in 55 seconds. What does this indicate about the air compressor's performance?Air Brake System Parts
  7. 57.A technician is inspecting a commercial vehicle's air brake system and notices that one of the air tanks has a small, continuous air leak around a weld seam. What is the most appropriate action to take?Air Brake System Parts
  8. 58.A driver is performing a pre-trip inspection on a commercial vehicle with a dual air brake system. What is the primary function of the check valve between the primary and secondary air tanks?Air Brake System Parts
  9. 59.A driver notices that after building full air pressure, the air compressor continues to run, but no air is being pumped into the air tanks. What is the most likely reason for this observation?Air Brake System Parts
  10. 60.A driver is conducting a pre-trip inspection of a commercial vehicle's air brake system. They notice that the supply pressure gauges for both the primary and secondary air tanks are fluctuating erratically, even when the engine RPM is steady and no brakes are being applied. What is the most probable cause?Air Brake System Parts
  11. 61.A driver hears a constant hissing sound coming from the area of the air compressor governor and notices that the air pressure in the tanks is not building up. What is the most probable cause?Air Brake System Parts
  12. 62.A commercial vehicle is equipped with a dual air brake system. A driver notices that after fully charging the system to 125 psi, the primary air tank loses pressure at a rate of 4 psi per minute with the engine off and brakes released, while the secondary tank holds steady at 125 psi. What does this indicate?Air Brake System Parts
  13. 63.A driver is inspecting a commercial vehicle equipped with a dual air brake system. They notice that the air pressure gauge for the primary air tank reads 125 psi, but the secondary air tank gauge reads only 70 psi. What is the most probable cause of this discrepancy?Air Brake System Parts
  14. 64.A driver is operating a commercial vehicle equipped with an Anti-lock Braking System (ABS). During an emergency stop on a slippery surface, the driver feels a pulsating sensation in the brake pedal. What does this indicate?Air Brake System Parts
  15. 65.A technician is diagnosing an issue where a commercial vehicle's spring brakes are not releasing properly, despite the air pressure being at normal operating levels and the parking brake control knob being pushed in. The technician suspects an issue with the parking brake control valve. What specific function of this valve might be failing?Air Brake System Parts
  16. 66.A driver is inspecting the air brake system on a commercial vehicle. They notice that the air compressor builds pressure from 85 psi to 125 psi in less than 45 seconds while the engine is idling. What does this indicate?Air Brake System Parts
  17. 67.A driver is operating an older commercial vehicle not equipped with an air dryer. To prevent air brake system issues in cold weather, which component is crucial for moisture management?Air Brake System Parts
  18. 68.A driver is performing a pre-trip inspection and notices that the brake drums on the drive axle are cracked. What type of brake component is the brake drum?Air Brake System Parts
  19. 69.A technician is diagnosing an issue where a commercial vehicle's air compressor takes an unusually long time to build up pressure from 0 psi to its cut-out pressure. All lines and fittings have been checked for leaks and found to be secure. What is the most likely cause?Air Brake System Parts
  20. 70.What is the primary purpose of the supply pressure gauges in a commercial vehicle equipped with an air brake system?Air Brake System Parts
  21. 71.A driver is performing a pre-trip inspection and notices that the air compressor is unusually noisy and vibrates excessively during operation. The air pressure is building normally. What is the most likely underlying issue?Air Brake System Parts
  22. 72.A technician is inspecting the air brake system of a commercial truck and observes that the safety valve on the wet air tank repeatedly opens when the air pressure reaches 150 psi. What does this indicate?Air Brake System Parts
  23. 73.An anti-lock braking system (ABS) is a critical safety feature in modern commercial vehicles. What is the primary function of ABS in an air brake system?Air Brake System Parts
  24. 74.A driver is inspecting a vehicle equipped with an anti-lock braking system (ABS). After starting the engine, the yellow ABS indicator light illuminates on the dashboard, then goes out after a few seconds. What does this indicate about the ABS?Air Brake System Parts
  25. 75.A driver observes that the parking brake control knob pops out automatically when the air pressure in the system drops to approximately 40 psi. What does this indicate?Air Brake System Parts
  26. 76.A driver is inspecting a truck and finds that the front brake limiting valve is set to 'low pressure' mode. Under what conditions should this setting typically be used?Air Brake System Parts
  27. 77.A commercial vehicle driver is performing a pre-trip inspection. After charging the system, they notice that the air compressor cycles on and off more frequently than usual, even when no brakes are being applied. What does this symptom most likely indicate?Air Brake System Parts
  28. 78.A driver performs a pre-trip inspection and tests the service brakes. They notice that when the brake pedal is pressed, the air pressure drops by approximately 5 psi, and then quickly recovers when the pedal is released. This process is repeated several times with consistent results. What does this indicate about the air brake system?Air Brake System Parts
  29. 79.A driver is operating a commercial vehicle equipped with an air brake system. They notice that the air compressor is constantly running and the air pressure gauges show that the system cannot build beyond 80 psi, even after several minutes of operation. What is the most probable cause of this issue?Air Brake System Parts
  30. 80.A commercial vehicle driver notices that during moderate braking, the front wheels tend to lock up prematurely, especially on slippery surfaces. The vehicle is equipped with a front brake limiting valve. What is the likely cause of this issue?Air Brake System Parts
  31. 81.A technician is troubleshooting a commercial vehicle's air brake system. They observe that when the service brakes are applied, one of the brake chambers has a significantly longer pushrod stroke than the others, exceeding the maximum allowable limit. What is the most likely consequence of this issue?Air Brake System Parts
  32. 82.A technician is troubleshooting a commercial vehicle and finds that the air compressor is constantly running, but the air pressure in the tanks never reaches the cut-out pressure. The safety valve on the air tank is not releasing air. What is the most likely cause?Air Brake System Parts
  33. 83.A driver is performing a brake test and notices that the red low air pressure warning light and buzzer activate when the air pressure drops to 70 psi. What does this indicate?Air Brake System Parts
  34. 84.A driver notices that when they apply the service brakes on a commercial vehicle, the brake pedal feels unusually soft and requires excessive travel before the brakes engage effectively. This issue is most likely related to which of the following?Air Brake System Parts
  35. 85.A commercial vehicle is equipped with an Anti-lock Braking System (ABS). During an emergency stop on a slippery surface, the driver feels a pulsating sensation in the brake pedal. What does this sensation indicate?Air Brake System Parts
  36. 86.A technician is troubleshooting a commercial vehicle's air brake system. They observe that even after the air compressor has built up to its maximum pressure, there is a continuous, loud hiss of air coming from a specific valve on one of the air tanks. What does this indicate?Air Brake System Parts
  37. 87.A driver is performing a pre-trip inspection on a commercial vehicle equipped with an Anti-lock Braking System (ABS). They notice that after turning the ignition key to the 'on' position, the amber ABS indicator light illuminates for a few seconds and then turns off. What does this indicate?Air Brake System Parts
  38. 88.A driver is inspecting the air storage tanks and notices that one of the tanks has a small dent, but no visible air leak. According to regulations, what is the most appropriate action for the driver to take?Air Brake System Parts
  39. 89.A technician is inspecting a commercial vehicle's air brake system. They observe that the air compressor governor consistently cuts out at 125 psi and cuts in at 100 psi. What is the primary function of the air compressor governor in this scenario?Air Brake System Parts
  40. 90.A driver is inspecting an older commercial vehicle not equipped with an air dryer. To prevent ice from forming in the air brake system, what component should be present and regularly maintained?Air Brake System Parts
  41. 91.A driver is performing a pre-trip inspection and notices that the brake drums on the drive axles are discolored (dark blue or purple) and show signs of cracking. What does this indicate?Air Brake System Parts
  42. 92.A driver is inspecting the air storage tanks on a commercial vehicle. They notice significant rust and pitting on the exterior of one of the tanks. What is the most appropriate action the driver should take?Air Brake System Parts
  43. 93.A driver is performing a pre-trip inspection on a commercial vehicle equipped with an air brake system. They notice that the air compressor builds air pressure from 85 psi to 125 psi in 40 seconds. What does this indicate about the air compressor's performance?Air Brake System Parts
  44. 94.A driver observes that when the air compressor builds pressure, it stops pumping air into the tanks once the pressure reaches 125 psi. What component is responsible for this action?Air Brake System Parts
  45. 95.A driver is performing an emergency stop in a commercial vehicle equipped with an Anti-lock Braking System (ABS). During the stop, they feel a rapid pulsing sensation in the brake pedal. What does this sensation indicate?Air Brake System Parts
  46. 96.A driver notices that the red low air pressure warning light and buzzer do not activate when the air pressure drops below 60 psi. However, the parking brake still automatically engages below 45 psi. What is the most likely issue?Air Brake System Parts
  47. 97.A driver is inspecting the air storage tanks on a commercial vehicle. They notice that the automatic drain valve on one of the tanks is continuously expelling air, even after the system has reached full pressure. What is the most likely consequence of this issue?Air Brake System Parts
  48. 98.A driver notices that the red low air pressure warning light and buzzer come on when the air pressure drops below 60 psi. However, the spring brakes do not automatically apply until the air pressure drops to 30 psi. What does this indicate regarding the vehicle's air brake system?Air Brake System Parts
  49. 99.A technician is performing a pre-trip inspection on a commercial vehicle. When testing the spring brakes, what action should the technician take to ensure they are functioning correctly?Air Brake System Parts
  50. 100.A driver is inspecting the air brake system and notices that the check valve between the primary and secondary air tanks is leaking. What is the primary risk associated with a leaking check valve in a dual air brake system?Air Brake System Parts