HEAVY TRUCK BRAKES MICHIGAN
MECHANIC STUDY GUIDE
AN ENGINE BRAKE (JACOBS BRAKE) - answerA. 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: - answerA. 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: - answerA.
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: - answerA.
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? - answerA. 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? - answerA. 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: - answerA. 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: -
answerA. A GOVENOR THAT IS BAD OR OUT OF ADJUSTMENT. (POSSIBLE
CORRECT AWNSER)
B. A PLUGGED SAFETY VALVE. (NOT CORRECT AWNSER)
C. A ONE-WAY CHECK VALVE STUCK OPEN.
D. A STICKY QUICK RELEASE VALVE.
IF GLADHAND 2 IS UNHOOKED OR HAS A SEVERE LEAK, WHAT WILL HAPPEN
DURING OPERATION? - answerA. VALVE AT A WILL PROTECT THE PRESSURE IN
THE DRY TANK.
B. TRACTOR BRAKES WILL APPLY AUTOMATICALLY. (NOT CORRECT AWNSER)
C. VALVE AT C WILL APPLY TRAILER BRAKES.
D. VALVE AT B WILL APPLY TRAILER BRAKES.
DURING A HARD STOP, ONE BRAKE HAS LOCKED ON A TRAILER WITH "S" CAM
BRAKES. THE SERVICE AND EMERGENCY LINES ARE HOOKED UP PROPERLY
AND THE SYSTEM IS AT NORMAL PRESSURE BUT THE BRAKES WILL NOT
RELEASE. WHAT IS THE LIKELY CAUSE OF THIS PROBLEM? - answerA. THE
SERVICE BRAKE CHAMBER DIAPHRAGM HAS SPLIT. (POSSIBLE CORRECT
AWNSER)
B. THE CAM HAS ROLLED OVER DUE TO TOO MUCH LINING WEAR.
C. THE ANTI-LOCK MODULE HAS BURNED OUT AT THE SENDING UNIT. (NOT
CORRECT AWNSER)
D. THE CHAMBER SPRING HAS RUSTED AND IS BROKEN.
TOO MUCH EFFORT IS REQUIRED ON THE BRAKE PEDAL TO STOP A TRUCK
WITH A VACUUM BOOSTER. WHAT IS THE LIKELY CAUSE OF THIS PROBLEM? -
answerA. SEIZED AUTOMATIC ADJUSTERS.
B. GLAZED LININGS
C. A DEFECTIVE MODULATOR VALVE. (NOT CORRECT AWNSER)
D. VERY HIGH ENGINE VACUUM. (POSSIBLE CORRECT AWNSER)
MECHANIC STUDY GUIDE
AN ENGINE BRAKE (JACOBS BRAKE) - answerA. 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: - answerA. 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: - answerA.
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: - answerA.
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? - answerA. 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? - answerA. 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: - answerA. 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: -
answerA. A GOVENOR THAT IS BAD OR OUT OF ADJUSTMENT. (POSSIBLE
CORRECT AWNSER)
B. A PLUGGED SAFETY VALVE. (NOT CORRECT AWNSER)
C. A ONE-WAY CHECK VALVE STUCK OPEN.
D. A STICKY QUICK RELEASE VALVE.
IF GLADHAND 2 IS UNHOOKED OR HAS A SEVERE LEAK, WHAT WILL HAPPEN
DURING OPERATION? - answerA. VALVE AT A WILL PROTECT THE PRESSURE IN
THE DRY TANK.
B. TRACTOR BRAKES WILL APPLY AUTOMATICALLY. (NOT CORRECT AWNSER)
C. VALVE AT C WILL APPLY TRAILER BRAKES.
D. VALVE AT B WILL APPLY TRAILER BRAKES.
DURING A HARD STOP, ONE BRAKE HAS LOCKED ON A TRAILER WITH "S" CAM
BRAKES. THE SERVICE AND EMERGENCY LINES ARE HOOKED UP PROPERLY
AND THE SYSTEM IS AT NORMAL PRESSURE BUT THE BRAKES WILL NOT
RELEASE. WHAT IS THE LIKELY CAUSE OF THIS PROBLEM? - answerA. THE
SERVICE BRAKE CHAMBER DIAPHRAGM HAS SPLIT. (POSSIBLE CORRECT
AWNSER)
B. THE CAM HAS ROLLED OVER DUE TO TOO MUCH LINING WEAR.
C. THE ANTI-LOCK MODULE HAS BURNED OUT AT THE SENDING UNIT. (NOT
CORRECT AWNSER)
D. THE CHAMBER SPRING HAS RUSTED AND IS BROKEN.
TOO MUCH EFFORT IS REQUIRED ON THE BRAKE PEDAL TO STOP A TRUCK
WITH A VACUUM BOOSTER. WHAT IS THE LIKELY CAUSE OF THIS PROBLEM? -
answerA. SEIZED AUTOMATIC ADJUSTERS.
B. GLAZED LININGS
C. A DEFECTIVE MODULATOR VALVE. (NOT CORRECT AWNSER)
D. VERY HIGH ENGINE VACUUM. (POSSIBLE CORRECT AWNSER)
