Which of the following could cause the brakes on a truck to wear too fast?
A. Glazed Drums
B. Wrong linings installed
C. Low air pressure in the service tanks
D. Governor cut-out pressure too high - Answers Answer A is incorrect. Glazed drum linings are hard
and do not wear. They also do not stop the truck.
Answer B is correct. The wrong lining for the application may be the problem.
Answer C is incorrect. Low air pressure in the tanks would not cause brake wear. It may cause a low
amount of reserve air in case of multiple brake applications.
Answer D is incorrect. High governor cut=out pressure may cause the safety valve to open, but would
not cause the brakes to wear too fast.
Which of the following could case one brake on a truck to wear faster than the others?
A. Mismatched service brake chambers
B. Mismatched parking brake chambers
C. Low air pressure in the service tanks
D. Governor cut-out pressure too low - Answers Answer A is correct. Mismatched brake service
chambers would apply unequal brake application pressure from side to side, which would cause one
brake to wear faster.
Answer B is incorrect. Mismatched parking brake chambers would not cause brake wear. It would
possibly allow the brake to roll when parked, because one side could have insufficient parking brake
application.
Answer C is incorrect. Low air pressure in the tanks would not cause brake wear. It may cause a low
amount of reserve air in case of multiple brake applications
Answer D is incorrect. Low governor cut-out pressure may cause an inadequate amount of air in
reserve but would not cause the brake to wear too fast.
There is an audible air leak from under the dash when the foot valve is applied. Technician A says the
double-check valve may be faulty. Technician B says the single-check valve may be
faulty. Who is correct? - Answers A. A only
B. B only
C. Both A and B
D. Neither A nor B
Answer A is correct. A leaking double check valve could allow air to flow to the foot valve and out the
open exhaust
Answer B is incorrect. Single check valves are used to protect the tanks. They do not cause an air leak
when the brakes are applied.
Answer C is incorrect. Technician B is incorrect.
Answer D is incorrect. Technician A is correct.
On a straight truck equipped with air brakes, the secondary tank pressure gauge falls to zero when
she wet air tank is drained. Technician A says the one-way check valve may be faulty.
Technician B says the foor valve may be faulty. Who is correct?
A. A only
B. B only
C. Both A and B
D. Neither A nor B - Answers Answer A is correct. The one way check valve should protect the
secondary tank. The check valve is leaking.
Answer B is incorrect. The foot valve does not separate the wet and secondary tanks.
Answer C is incorrect. Technician B is incorrect.
Answer D is incorrect. Technician A is correct.
Which of the following could set an antilock braking system (ABS) wheel speed sensor code:
A. Faulty modulator hold solenoid
B. Faulty modulator release solenoid
C. Incorrect wheel bearing adjustment
D. Incorrect brake adjustment - Answers Answer A is incorrect. A faulty solenoid would not cause a
wheel speed sensor code. It could cause a modulator valve code.
, Answer B is incorrect. A faulty solenoid would not cause a wheel speed sensor code. It could cause a
modulator valve code
Answer C is correct. A loose wheel bearing adjustment can cause a faulty wheel speed sensor and a
wheel speed sensor code.
Answer D is incorrect. An incorrect brake adjustment may cause a dragging brake but would not cause
a wheel speed sensor code
The air drier purged too often. Technician A says the air drier delivery check valve may be leaking.
Technician B says a leaking wet tank could be the cause. Who is correct?
A. A only
B. B only
C. Both A and B
D. Neither A nor B - Answers Answer A is incorrect. Technician B is also correct.
Answer B is incorrect. Technician A is also correct.
Answer C is correct. A leaking air drier check valve will allow the wet tank to drain back through the
air drier. This will cause air pressure to drop to governor cut-in rapidly. The air compressor will again
build tank pressure and unload, and the sequence will start over. A leaking wet tank will cause the air
pressure to fall rapidly and the compressor to build air again and then cut out. This too will cause the
air drier to purge often.
Answer D is incorrect. Both technicians are correct.
The safety valve releases on the air tank. Which of the following is the most likely cause?
A. Plugged line from the supply tank to the governor
B. Faulty tractor protection valve
C. Stuck spitter on the air drier
D. Faulty secondary tank - Answers Answer A is correct. If the line from the supply tank to the
governor were plugged the governor would not unload the compressor.
Answer B is incorrect. The tractor protection valve could not cause excessive pressure.
Answer C is incorrect. A stuck spitter would prevent the air drier from purging.
Answer D is incorrect. A faulty secondary tank could leak, but that would not cause excessive air
pressure.
A truck with hydraulic disc/drum brakes has a high firm pedal with poor stopping. Which of the
following could be the cause?
A. The brakes are adjusted too loose.
B. The brake linings are glazed.
C. The brake pedal pushrod is too long.
D. The driveline parking brake is misadjusted. - Answers Answer A is incorrect. If drum brakes are
adjusted too loose the pedal will be low because the pedal will need to travel farther to take up the
clearance.
Answer B is correct. Glazed brake linings will not create the friction needed to stop the truck but will
allow the pedal to feel high and firm.
Answer C is incorrect. A pushrod that is too long would cause the brakes to drag.
Answer D is incorrect. The driveline parking brake adjustment would not cause a low pedal. It is not
connected to the service brakes.
Air pressure builds up on a truck in 1.5 minutes. The specification manual says it should take 3.5
minutes. Technician A says the air tanks could have water buildup. Technician B says the air tanks
could have oil buildup. Who is correct?
A. A only
B. Bonly
C. Both A and B
D. Neither A nor B - Answers Answer A is incorrect. Both technicians are correct.
Answer B is incorrect. Both technicians are correct.
Answer C is correct. Oil or water buildup will reduce the volume and result in a decreased air buildup
time.
Answer D is incorrect. Both technicians are correct.
Brake fluid is leaking from the rear of a master cylinder on a truck equipped with hydro-boost brakes.
Which of the following is the most likely cause?
A. By-passing master cylinder
B. Primary seal leaking