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CDL Air Brakes Test practice questions

252 free questions with answers and explanations.

Practice test
  1. 151.A technician is inspecting the brake linings on a commercial vehicle with air brakes. They notice that the linings on one wheel are covered in grease or oil. What is the most significant consequence of this condition?Inspecting Air Brake Systems
  2. 152.During a pre-trip inspection, a driver observes that the air pressure gauge shows 80 psi while the parking brake is set and the engine is off. The low air warning light is illuminated. What is the immediate correct action the driver should take?Inspecting Air Brake Systems
  3. 153.A driver is performing a governor cut-in/cut-out test. The air compressor should cut in when the air pressure drops to approximately what PSI, and cut out when it reaches approximately what PSI?Inspecting Air Brake Systems
  4. 154.A driver is inspecting the brake linings on a commercial vehicle with air brakes. What is the minimum acceptable thickness for brake linings on most heavy-duty vehicles?Inspecting Air Brake Systems
  5. 155.A driver is performing a functional check of the parking brake on a tractor-trailer. After building full air pressure, setting the parking brake, and putting the vehicle in a low gear, the driver gently pulls against the brake. The vehicle should:Inspecting Air Brake Systems
  6. 156.A driver is performing a pre-trip inspection and notices that a brake chamber on one of the drive axles has a significant bulge in its diaphragm. What action should the driver take?Inspecting Air Brake Systems
  7. 157.During a pre-trip inspection, a driver checks the air lines for proper connection and condition. What type of damage to an air line is most likely to cause a slow, continuous air leak that might only be noticeable over time?Inspecting Air Brake Systems
  8. 158.A driver is performing a pre-trip inspection on a tractor-trailer. After ensuring the air system is fully charged (125 psi), they shut off the engine, release the parking brake, and chock the wheels. They then allow the air pressure to stabilize. After one minute, the air pressure has dropped to 121 psi. What does this indicate?Inspecting Air Brake Systems
  9. 159.A driver is inspecting the air tanks on a commercial vehicle. What is the primary purpose of regularly draining the air tanks?Inspecting Air Brake Systems
  10. 160.A technician is inspecting a vehicle's air brake system and finds that one of the brake chambers has a dented pushrod. What is the primary concern with this condition?Inspecting Air Brake Systems
  11. 161.A driver is inspecting the air compressor's drive belt. Which of the following conditions would require immediate attention or replacement of the belt?Inspecting Air Brake Systems
  12. 162.A driver is performing a pre-trip inspection and observes that the brake pushrod on a service brake chamber moves more than 1 inch when the service brakes are applied. What does this excessive movement indicate?Inspecting Air Brake Systems
  13. 163.A driver is performing a pre-trip inspection on a vehicle with air brakes. They notice that the air pressure gauge reads 60 psi when the low air pressure warning light and buzzer activate. The vehicle is equipped with a 'wig-wag' type warning device. What does this observation indicate?Inspecting Air Brake Systems
  14. 164.A driver is inspecting the brake drums on a vehicle equipped with air brakes. Which of the following conditions would NOT require the brake drum to be replaced?Inspecting Air Brake Systems
  15. 165.A driver is performing a pre-trip inspection on a tractor-trailer combination. After charging the air system to 125 psi, they shut off the engine, release the parking brake, and chock the wheels. They then fully apply the service brake pedal for one minute. The air pressure drops from 125 psi to 118 psi. What action should the driver take?Inspecting Air Brake Systems
  16. 166.A driver is performing a pre-trip inspection on a vehicle equipped with air brakes. They notice that a brake chamber pushrod on one wheel is bent. The air pressure in the system is normal. What is the most immediate concern regarding this bent pushrod?Inspecting Air Brake Systems
  17. 167.During a pre-trip inspection, a driver observes excessive moisture and oil residue when draining the air tanks. What does this indicate about the air compressor?Inspecting Air Brake Systems
  18. 168.A driver is performing a pre-trip inspection and observes that the brake linings on a wheel are contaminated with oil or grease. What is the most significant consequence of this contamination?Inspecting Air Brake Systems
  19. 169.A technician is performing a diagnostic check on an air brake system. They notice that the air compressor struggles to build pressure, and when it finally reaches cut-out pressure, it takes an excessively long time (more than 3 minutes to go from 85 to 100 psi). What is the most likely cause?Inspecting Air Brake Systems
  20. 170.A driver is performing a pre-trip inspection on a vehicle with air brakes. They notice that the air compressor's discharge line, connecting the compressor to the first air tank, is coated in oil. What is the most likely cause of this observation?Inspecting Air Brake Systems
  21. 171.A driver is inspecting the brake pushrods and slack adjusters on a vehicle equipped with air brakes. They notice that a slack adjuster on a service brake chamber is bent. What is the primary concern with a bent slack adjuster?Inspecting Air Brake Systems
  22. 172.A commercial driver is checking the brake adjustment on S-cam air brakes. What is the maximum acceptable free play for a properly adjusted manual slack adjuster?Using Air Brakes
  23. 173.A driver needs to make an emergency stop in a commercial vehicle equipped with air brakes and Anti-lock Braking System (ABS). What is the correct procedure for braking with ABS in an emergency?Using Air Brakes
  24. 174.A driver needs to park a commercial vehicle equipped with air brakes on a slight downgrade. In addition to engaging the parking brake, what other essential safety measure should be taken?Using Air Brakes
  25. 175.A commercial driver is operating a vehicle equipped with air brakes on a very slippery road. They need to slow down quickly but safely. The vehicle does NOT have ABS. Which braking technique would be most appropriate?Using Air Brakes
  26. 176.A driver is preparing to descend a long, steep downgrade in a heavy commercial vehicle equipped with air brakes. To prevent brake fade, what is the most appropriate braking strategy?Using Air Brakes
  27. 177.A commercial driver is performing a pre-trip inspection and notices that the air compressor's automatic shut-off occurs at 125 psi, but it doesn't restart until the pressure drops to 85 psi. What component is likely malfunctioning?Using Air Brakes
  28. 178.When checking the slack adjusters on S-cam brakes, what is the maximum amount of free play or movement allowed at the pushrod when the brakes are NOT applied?Using Air Brakes
  29. 179.During a pre-trip inspection, a commercial driver checks the air tanks (reservoirs). What is the primary purpose of these tanks in an air brake system?Using Air Brakes
  30. 180.A driver is operating a commercial vehicle with air brakes and needs to make an emergency stop on a dry, level road. The vehicle is equipped with ABS. What is the most effective braking technique in this situation?Using Air Brakes
  31. 181.The air brake system relies on several main components to function. Which of the following is responsible for storing the compressed air used for braking?Using Air Brakes
  32. 182.A commercial driver is operating a vehicle equipped with air brakes. They need to brake suddenly to avoid an obstacle but want to maintain steering control. If the vehicle is NOT equipped with ABS, which braking technique is most appropriate?Using Air Brakes
  33. 183.A commercial driver notices that their vehicle's air pressure gauge builds from 85 psi to 125 psi in 30 seconds. The vehicle is a single unit, and the engine is at operating RPM. What does this indicate about the air compressor's recovery rate?Using Air Brakes
  34. 184.A fully loaded commercial vehicle with air brakes is traveling at 55 mph. The driver needs to make an emergency stop on dry pavement. Assuming good brakes and driver reaction, approximately how far will the vehicle travel from the moment the driver perceives the need to stop until the vehicle comes to a complete halt?Using Air Brakes
  35. 185.A commercial driver is operating a tractor-trailer on a long, steep downgrade. The vehicle is equipped with air brakes. To prevent brake fade and maintain control, which braking technique should the driver primarily employ?Using Air Brakes
  36. 186.A commercial driver observes that their vehicle's air pressure gauge is showing a rapid drop in pressure when the brake pedal is pressed and held, but the vehicle is not stopping as expected. This condition is most indicative of:Using Air Brakes
  37. 187.A commercial driver is performing a pre-trip inspection of their air brake system. They notice that the air compressor cuts out at 125 psi and cuts back in at 100 psi. What does this indicate about the air compressor governor?Using Air Brakes
  38. 188.A commercial vehicle with air brakes is traveling at 45 mph on a dry, level road. The driver needs to perform an emergency stop. What is the approximate total stopping distance for this vehicle?Using Air Brakes
  39. 189.A driver is operating a commercial vehicle with air brakes on a long, steep downgrade. To prevent brake fade and maintain control, what braking technique should be primarily used?Using Air Brakes
  40. 190.A driver is performing a normal stop in a commercial vehicle equipped with air brakes. Which of the following is the most accurate description of the typical air pressure required for a full brake application?Using Air Brakes
  41. 191.A commercial driver is performing a pre-trip inspection. They pump the brake pedal several times to reduce air pressure. The spring brakes (parking/emergency brakes) should automatically engage when the air pressure drops to a specific range. What is this typical pressure range for automatic spring brake application?Using Air Brakes
  42. 192.A driver is operating a commercial vehicle on a very slippery road and needs to slow down. To maintain steering control and prevent a skid, which braking technique should be primarily used if the vehicle does NOT have ABS?Using Air Brakes
  43. 193.A driver is attempting to stop a commercial vehicle with air brakes and notices a significant delay between pressing the brake pedal and the brakes actually engaging. This phenomenon is known as:Using Air Brakes
  44. 194.During a pre-trip inspection, a driver tests the service brakes on a commercial vehicle with air brakes by applying full pressure for one minute. The air pressure drop should not exceed a certain amount. For a combination vehicle, what is the maximum allowable air pressure drop in one minute?Using Air Brakes
  45. 195.A commercial driver is conducting a pre-trip inspection of their air brake system. They notice that the low air pressure warning light and buzzer activate when the air pressure drops to 70 psi. What is the minimum air pressure at which these warnings MUST activate according to regulations?Using Air Brakes
  46. 196.During a pre-trip inspection, a driver checks the air brake system for leaks. With the engine off and the brakes applied, the air pressure loss rate should not exceed a certain amount. For a single vehicle, what is the maximum permissible air pressure drop in one minute?Using Air Brakes
  47. 197.A driver is operating a commercial vehicle with air brakes on a slippery road. To prevent skidding and maintain control during a moderate stop, which braking technique should be used, assuming the vehicle does NOT have ABS?Using Air Brakes
  48. 198.A commercial vehicle driver needs to park their air-braked vehicle on a slight upgrade. After stopping and setting the parking brake, what additional safety measure should be taken?Using Air Brakes
  49. 199.A commercial driver is conducting a pre-trip inspection of their air brake system. They observe that the air pressure in the primary and secondary tanks is at 125 psi. What is the typical range for the governor to cut-out the air compressor?Using Air Brakes
  50. 200.A driver is parking a commercial vehicle equipped with air brakes on a level surface. After securing the vehicle, what is the correct sequence for applying the parking brake and shutting down the engine?Using Air Brakes