1 | Page
HEAVY TRUCK BRAKES MICHIGAN
MECHANIC STUDY GUIDE Questions and
Answers
AN ENGINE BRAKE (JACOBS BRAKE)
Ans: 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 BUILD UP OF 30-45 LBS
OF PRESSURE.
D. OPENS THE EXHAUST VALVES NEAR THE TOP OF THE COMPRESSION
STROKE TO RELEASE THE COMPRESSED AIR. (CORRECT AWNSER)
IN THE SYSTEM SHOWN BELOW, THE PART AT C IS:
Ans: A. AN INVERSION VALVE. (POSSIBLE CORRECT AWNSER)
B. A SAFETY VALVE.
C. A MODULATOR VALVE. (NOT CORRECT AWNSER)
D. A RELAY VALVE.
A MECHANIC HAS REMOVED A BRAKE DRUM AND FOUND THE
BRAKE LININGS SOAKED WITH GREASE. THE BRAKE LININGS
SHOULD BE:
Ans: A. REPLACED. (CORRECT AWNSER)
B. SANDED TO ROUGHEN UP THE FRICTION SURFACE.
C. DIPPED IN LACQUER THINNER.
D. WASHED WITH DENATURED ALCOHOL.
IN THE DRAWING BELOW, THE PARKING BRAKES ARE APPLIED
BY:
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, 2 | Page
Ans: A. AIR PRESSURE AT POINT F.
B. VACUUM IN AREA B.
C. SPRING AT POINT C.
D. PRESSURE IN AREA A. (NOT CORRECT AWNSER)
WHAT IS THE PURPOSE OF A VACUUM BOOSTER?
Ans: A. TO DECREASE BRAKE PEDAL EFFORT. (POSSIBLE CORRECT
AWNSER)
B. TO PREVENT FADE UNDER HEAVY BRAKING.
C. TO PROVIDE ASSISTANCE WHEN THE ENGINE VACUUM IS LOW. (NOT
CORRECT AWNSER)
D. TO MAINTAIN UNIFORM PEDAL TRAVEL AS THE LININGS WEAR.
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?
Ans: 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 AWNSER)
THE RESIDUAL VALVE IN THE MASTER CYLINDER:
Ans: A. LIMITS PRESSURE BUILD UP IN THE SYSTEM.
B. STOPS THE FLOW TO DAMAGED BRAKE LINES.
C. KEEPS SOME PRESSURE IN THE SYTEM WHEN THE BRAKES ARE
RELEASED. (CORRECT AWNSER)
D. IS OPERATED BY ENGINE VACUUM.
HIGHER THAN NORMAL AIR PRESSURE WOULD LIKELY BE
CAUSED BY:
© 2025 All rights reserved
HEAVY TRUCK BRAKES MICHIGAN
MECHANIC STUDY GUIDE Questions and
Answers
AN ENGINE BRAKE (JACOBS BRAKE)
Ans: 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 BUILD UP OF 30-45 LBS
OF PRESSURE.
D. OPENS THE EXHAUST VALVES NEAR THE TOP OF THE COMPRESSION
STROKE TO RELEASE THE COMPRESSED AIR. (CORRECT AWNSER)
IN THE SYSTEM SHOWN BELOW, THE PART AT C IS:
Ans: A. AN INVERSION VALVE. (POSSIBLE CORRECT AWNSER)
B. A SAFETY VALVE.
C. A MODULATOR VALVE. (NOT CORRECT AWNSER)
D. A RELAY VALVE.
A MECHANIC HAS REMOVED A BRAKE DRUM AND FOUND THE
BRAKE LININGS SOAKED WITH GREASE. THE BRAKE LININGS
SHOULD BE:
Ans: A. REPLACED. (CORRECT AWNSER)
B. SANDED TO ROUGHEN UP THE FRICTION SURFACE.
C. DIPPED IN LACQUER THINNER.
D. WASHED WITH DENATURED ALCOHOL.
IN THE DRAWING BELOW, THE PARKING BRAKES ARE APPLIED
BY:
© 2025 All rights reserved
, 2 | Page
Ans: A. AIR PRESSURE AT POINT F.
B. VACUUM IN AREA B.
C. SPRING AT POINT C.
D. PRESSURE IN AREA A. (NOT CORRECT AWNSER)
WHAT IS THE PURPOSE OF A VACUUM BOOSTER?
Ans: A. TO DECREASE BRAKE PEDAL EFFORT. (POSSIBLE CORRECT
AWNSER)
B. TO PREVENT FADE UNDER HEAVY BRAKING.
C. TO PROVIDE ASSISTANCE WHEN THE ENGINE VACUUM IS LOW. (NOT
CORRECT AWNSER)
D. TO MAINTAIN UNIFORM PEDAL TRAVEL AS THE LININGS WEAR.
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?
Ans: 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 AWNSER)
THE RESIDUAL VALVE IN THE MASTER CYLINDER:
Ans: A. LIMITS PRESSURE BUILD UP IN THE SYSTEM.
B. STOPS THE FLOW TO DAMAGED BRAKE LINES.
C. KEEPS SOME PRESSURE IN THE SYTEM WHEN THE BRAKES ARE
RELEASED. (CORRECT AWNSER)
D. IS OPERATED BY ENGINE VACUUM.
HIGHER THAN NORMAL AIR PRESSURE WOULD LIKELY BE
CAUSED BY:
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