HEAVY TRUCK BRAKES MICHIGAN
MECHANIC STUDY GUIDE 2026
UPDATED ACTUAL EXAM WITH
CORRECT SOLUTIONS.
1. An engine brake (Jacobs brake):
A. Is a self-energizing servo type.
B. Is normally used in place of a spring brake.
C. Restricts the intake port and causes a buildup of 30–45
lbs of pressure.
D. Opens the exhaust valves near the top of the
compression stroke to release the compressed air.
Correct Answer: D. Opens the exhaust valves near the
top of the compression stroke to release the compressed
air.
2. In the system shown below, the part at C is:
A. An inversion valve.
B. A safety valve.
C. A modulator valve.
D. A relay valve.
Correct Answer: A. An inversion valve.
3. A mechanic has removed a brake drum and found the
brake linings soaked with grease. The brake linings
, should be:
A. Replaced.
B. Sanded to roughen up the friction surface.
C. Dipped in lacquer thinner.
D. Washed with denatured alcohol.
Correct Answer: A. Replaced.
4. In the drawing below, the parking brakes are applied
by:
A. Air pressure at point F.
B. Vacuum in area B.
C. Spring at point C.
D. Pressure in area A.
Correct Answer: C. Spring at point C.
5. What is the purpose of a vacuum booster?
A. To decrease brake pedal effort.
B. To prevent fade under heavy braking.
C. To provide assistance when the engine vacuum is low.
D. To maintain uniform pedal travel as the linings wear.
Correct Answer: A. To decrease brake pedal effort.
6. The trailer brakes do not work. The tractor system is
at normal pressure. There are no leaks and the service
and emergency lines are hooked up right. What could
cause this problem?
A. Ice in the lines at the trailer.
, B. A bad relay valve.
C. A bad safety relief valve.
D. Both A and B.
Correct Answer: D. Both A and B.
7. The residual valve in the master cylinder:
A. Limits pressure buildup in the system.
B. Stops the flow to damaged brake lines.
C. Keeps some pressure in the system when the brakes
are released.
D. Is operated by engine vacuum.
Correct Answer: C. Keeps some pressure in the system
when the brakes are released.
8. Higher than normal air pressure would likely be
caused by:
A. A governor that is bad or out of adjustment.
B. A plugged safety valve.
C. A one-way check valve stuck open.
D. A sticky quick-release valve.
Correct Answer: A. A governor that is bad or out of
adjustment.
9. If gladhand 2 is unhooked or has a severe leak, what
will happen during operation?
A. Valve at A will protect the pressure in the dry tank.
B. Tractor brakes will apply automatically.
MECHANIC STUDY GUIDE 2026
UPDATED ACTUAL EXAM WITH
CORRECT SOLUTIONS.
1. An engine brake (Jacobs brake):
A. Is a self-energizing servo type.
B. Is normally used in place of a spring brake.
C. Restricts the intake port and causes a buildup of 30–45
lbs of pressure.
D. Opens the exhaust valves near the top of the
compression stroke to release the compressed air.
Correct Answer: D. Opens the exhaust valves near the
top of the compression stroke to release the compressed
air.
2. In the system shown below, the part at C is:
A. An inversion valve.
B. A safety valve.
C. A modulator valve.
D. A relay valve.
Correct Answer: A. An inversion valve.
3. A mechanic has removed a brake drum and found the
brake linings soaked with grease. The brake linings
, should be:
A. Replaced.
B. Sanded to roughen up the friction surface.
C. Dipped in lacquer thinner.
D. Washed with denatured alcohol.
Correct Answer: A. Replaced.
4. In the drawing below, the parking brakes are applied
by:
A. Air pressure at point F.
B. Vacuum in area B.
C. Spring at point C.
D. Pressure in area A.
Correct Answer: C. Spring at point C.
5. What is the purpose of a vacuum booster?
A. To decrease brake pedal effort.
B. To prevent fade under heavy braking.
C. To provide assistance when the engine vacuum is low.
D. To maintain uniform pedal travel as the linings wear.
Correct Answer: A. To decrease brake pedal effort.
6. The trailer brakes do not work. The tractor system is
at normal pressure. There are no leaks and the service
and emergency lines are hooked up right. What could
cause this problem?
A. Ice in the lines at the trailer.
, B. A bad relay valve.
C. A bad safety relief valve.
D. Both A and B.
Correct Answer: D. Both A and B.
7. The residual valve in the master cylinder:
A. Limits pressure buildup in the system.
B. Stops the flow to damaged brake lines.
C. Keeps some pressure in the system when the brakes
are released.
D. Is operated by engine vacuum.
Correct Answer: C. Keeps some pressure in the system
when the brakes are released.
8. Higher than normal air pressure would likely be
caused by:
A. A governor that is bad or out of adjustment.
B. A plugged safety valve.
C. A one-way check valve stuck open.
D. A sticky quick-release valve.
Correct Answer: A. A governor that is bad or out of
adjustment.
9. If gladhand 2 is unhooked or has a severe leak, what
will happen during operation?
A. Valve at A will protect the pressure in the dry tank.
B. Tractor brakes will apply automatically.
