T4 ASE BRAKES
(MEDIUM/HEAVY DUTY
BRAKES) EXAM
1. What is the primary function of a slack adjuster in an air brake system?
Answer: To maintain proper brake shoe-to-drum clearance and adjust for brake
lining wear.
2. What PSI range should a fully charged air system be at in a heavy-duty truck?
Answer: 100–125 PSI.
3. Why is it important to drain moisture from air reservoirs?
Answer: To prevent water from freezing and causing brake system malfunctions.
4. What component converts air pressure into mechanical force to apply the brakes?
Answer: Brake chamber.
5. What is the purpose of a compressor unloader?
Answer: To stop compressing air once the system reaches cut-out pressure, reducing
engine load.
,6. What does a governor do in an air brake system?
Answer: Controls when the air compressor cuts in and cuts out.
7. What should the maximum air leakage rate be in a static test (engine off, brakes
released)?
Answer: Approximately 2 PSI per minute.
8. What is a “foundation brake”?
Answer: The complete assembly that provides stopping action (drums, shoes,
hardware, chambers).
9. How often should air brake pushrods be checked for travel?
Answer: During regular inspections or when abnormal braking is suspected.
10. What does ABS stand for?
Answer: Anti-lock Braking System.
11. Why would an air dryer be used on a brake system?
Answer: To remove moisture and contaminants from compressed air.
12. A low air warning should activate before pressure drops below:
Answer: 60 PSI.
13. What does a dual air system mean?
, Answer: Two separate air circuits, usually one for front brakes and one for rear.
14. What is the purpose of brake fade testing?
Answer: To evaluate the braking system’s performance under high heat and
repeated stops.
15. What is the correct brake chamber pushrod travel when properly adjusted?
Answer: No more than 1 inch of travel at full brake application.
16. What happens if slack adjusters are not adjusted properly?
Answer: Increased stopping distances and uneven braking.
17. Which brake valve controls air pressure to the trailer brakes?
Answer: Trailer brake hand valve or relay valve (depending on system design).
18. What is the purpose of a spring brake in air brake systems?
Answer: To provide parking and emergency braking.
19. What is the common cause of spongy air brake feel?
Answer: Excessive air volume in brake chambers or air lines (possible leak).
20. Why is brake shoe contamination bad?
Answer: It decreases friction and reduces braking effectiveness.
(MEDIUM/HEAVY DUTY
BRAKES) EXAM
1. What is the primary function of a slack adjuster in an air brake system?
Answer: To maintain proper brake shoe-to-drum clearance and adjust for brake
lining wear.
2. What PSI range should a fully charged air system be at in a heavy-duty truck?
Answer: 100–125 PSI.
3. Why is it important to drain moisture from air reservoirs?
Answer: To prevent water from freezing and causing brake system malfunctions.
4. What component converts air pressure into mechanical force to apply the brakes?
Answer: Brake chamber.
5. What is the purpose of a compressor unloader?
Answer: To stop compressing air once the system reaches cut-out pressure, reducing
engine load.
,6. What does a governor do in an air brake system?
Answer: Controls when the air compressor cuts in and cuts out.
7. What should the maximum air leakage rate be in a static test (engine off, brakes
released)?
Answer: Approximately 2 PSI per minute.
8. What is a “foundation brake”?
Answer: The complete assembly that provides stopping action (drums, shoes,
hardware, chambers).
9. How often should air brake pushrods be checked for travel?
Answer: During regular inspections or when abnormal braking is suspected.
10. What does ABS stand for?
Answer: Anti-lock Braking System.
11. Why would an air dryer be used on a brake system?
Answer: To remove moisture and contaminants from compressed air.
12. A low air warning should activate before pressure drops below:
Answer: 60 PSI.
13. What does a dual air system mean?
, Answer: Two separate air circuits, usually one for front brakes and one for rear.
14. What is the purpose of brake fade testing?
Answer: To evaluate the braking system’s performance under high heat and
repeated stops.
15. What is the correct brake chamber pushrod travel when properly adjusted?
Answer: No more than 1 inch of travel at full brake application.
16. What happens if slack adjusters are not adjusted properly?
Answer: Increased stopping distances and uneven braking.
17. Which brake valve controls air pressure to the trailer brakes?
Answer: Trailer brake hand valve or relay valve (depending on system design).
18. What is the purpose of a spring brake in air brake systems?
Answer: To provide parking and emergency braking.
19. What is the common cause of spongy air brake feel?
Answer: Excessive air volume in brake chambers or air lines (possible leak).
20. Why is brake shoe contamination bad?
Answer: It decreases friction and reduces braking effectiveness.
