MB Air Brake Test 13 2025

1. What function does the tractor protection system serve?
2. When the driver releases the foot valve treadle in a vehicle without quick release valves, where would the application/service air from the brake chambers go?
3. What issue does a broken return spring in the tractor protection valve cause?
4. What is the main purpose of the trailer hand valve?
5. Securing glad hands and coupler lines helps prevent what from happening?
6. What term is used to denote the scenario when the tractor is operated without a trailer attached?
7. Can the driver still use the foot valve once a trailer brake application is initiated via the hand valve?
8. Approximately how many psi in the supply line are necessary to open the tractor protection valve, which is spring-loaded?
9. The tractor protection system comprises how many valves?
10. How many lines feed the tractor protection valve?
11. If a tractor-trailer didn't have a tractor protection system, what could go wrong?
12. What is the most widely used type of trailer supply valve?
13. Which of the following is false? A trailer with two axles and spring parking brakes has
14. A sudden air loss in the supply line has triggered the relay emergency valve to activate the trailer emergency brakes. They will remain applied until
15. When the foot valve is released and the hand valve is activated, what is the result?
16. Which of the following is not a key function of the trailer spring parking brake valve?
17. If the primary reservoir's air pressure drops, is there enough pressure left for a few brake applications before the spring parking brakes are activated?
18. What action must be taken with the trailer supply valve in the event of tractor reservoir air loss?
19. From where is blended air drawn in a dual brake system?
20. If the control line is ruptured or disconnected, when will action take place?
21. A sudden air loss in the supply line has triggered the relay emergency valve to activate the trailer emergency brakes. How long can the system keep applying the brakes?
22. Which statement is not true? The trailer brakes will stay applied until...
23. If there's a loss of reservoir air pressure, what prevents the reservoir air pressure in the primary reservoir from escaping back to the supply reservoir and the ruptured line?
24. What is the role of spring parking brakes in a trailer?
25. What is not a function of the relay emergency valve?
26. What types of trailers typically have a manual supply valve?
27. What are the two positions that the manual trailer supply valve can occupy?
28. What happens when the foot or hand valve is released during a brake application?
29. Where would air pressure be lost if the compressor discharge line is ruptured?
30. What has been added to minimize trailer brake lag time during foot or hand valve brake application?
31. When should the trailer supply valve be open in terms of tractor pressure?
32. For a dual air brake system, what does each section of the dual foot valve control?
33. What occurs when there is a sudden loss of air pressure in the supply line, triggering the relay emergency valve?
34. If the relay emergency valve has applied the trailer brakes in an emergency, what must be done to move the trailer?
35. With a dual air brake system, when will the vehicle lose its braking ability?
36. What system are most heavy vehicles currently using?
37. What does it mean to 'charge' the trailer system?
38. Should you use trailer air brakes to secure a parked vehicle left unattended?
39. What initiates the application of spring parking brakes?
40. What would happen if a trailer, not equipped with spring parking brakes, separated from the tractor?
41. How is the foot valve divided in a dual air brake system?
42. What should always be used as a safety measure when parking trailers without spring parking brakes?
43. At what point do the low air pressure warning devices get activated in the primary and secondary circuits?
44. ABS wheel sensors are found on at least how many sets of wheels?
45. Is automatic traction control found in every vehicle?
46. Which statement is incorrect? When all air is lost and the spring brakes have applied, the vehicle can be moved by...
47. How should a vehicle equipped with ABS be driven differently from others?
48. What does the ABS do when a slippery road surface causes engine brake to be engaged?
49. What is sourced to supply the spring parking brake control valve?
50. If a failure occurs in the primary circuit, at what pressure does the spring parking brake control valve exhaust the remaining air in the secondary circuit?