TESTED QUESTIONS
◉ 3. Which of the following cannot cause a drum on an air - braked
vehicle to overheat ?
A. an over - tightened brake adjuster at that wheel
B. under - adjusted brake ( s ) elsewhere on the vehicle
C. too - high governor cut - out pressure
D. driving downhill in too high a gear.. Answer: 3. The correct answer
is C. The governor controls the air compressor output by unloading
or cycling it . It has no direct effect on the mechanical brake parts .
While the pressure setting is important to maintain air brake system
pressure within acceptable limits , an incorrect setting will not cause
the drum on an air - braked vehicle to overheat . All other choices
given , however , will cause overheating problems .
◉ 4. All the brakes drag on a truck with hydraulic brakes . Which of
the following could be the cause ? A. air in the hydraulic system
B. too high a vacuum supply to the power brake booster
C. a leaking secondary cup in the master cylinder
D. no brake pedal free travel. Answer: 4. The correct answer is D.
Only a brake pedal with no free travel will cause all of the brakes to
drag . Answer A - air in the hydraulic system , will cause a spongy
pedal , while answer B - too high a vacuum to the power booster ,
,won't affect brake drag at all . Answer C , a leaking secondary cup in
the master cylinder , could increase pedal travel , but won't cause the
brakes to drag .
◉ 5. Which of the following could cause a pulsating brake pedal on a
truck with hydraulic brakes ?
A. zero brake pedal free travel
B. glazed linings
C. an out - of - round brake drum
D. a frozen wheel cylinder piston.. Answer: 5. The correct answer is
C. Of the choices given , only an out - of - round brake drum can
cause pulsation in a hydrau lic brake system . Answer A , zero brake
pedal free travel , will cause a dragging brake condition , but not
pulsation . Answer B , glazed linings , will affect stopping
performance and noise , and answer D , a frozen wheel cylinder , will
de grade stopping performance , but will not cause pulsation.
◉ 6. Air pressure gauges change an air pressure signal into an
electronic voltage signal using which of the following components ?
A. inductor
B. capacitor
C. transducer
D. regulator. Answer: 6. The correct answer is C. An element inside
an air pressure transducer responds to air pressure increase or
decrease, and the transducer converts that pressure differentiation
,into a voltage signal, which is displayed in a proportionate reading
on the dash gauge.
◉ 7. Technician A says that linings worn too thin on an air - braked
vehicle can cause the S - camshaft to roll over . Technician B says this
condition can cause excess brake pedal travel . Who is right ?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B. Answer: 7. The correct answer is A. The brake
adjuster is connected to a shaft that runs perpendicular to the plane
formed by the pushrod and slack adjuster. As the pushrod is
extended, the shaft rotates. The shaft, in turn, is connected to an S-
shaped cam between the brake shoes. As the shaft rotates, so does
the cam. The brake shoes are forced apart and against the brake
drum, creating the friction needed to slow the vehicle. Thin brake
linings can allow the S-cam to roll over, but will not affect brake
pedal travel.
◉ 8. Spring brakes on an air - braked vehicle must be able to hold
the vehicle facing uphill or downhill on what percent grade ?
A. 10 %
B. 20 %
C. 30 %
, D. 40 %. Answer: 8. The correct answer is B. Per Federal Motor
Vehicle Safety Standard (FMVSS) 121, the parking brakes must be
able to hold a vehicle, loaded to its gross weight rating, stationary on
a smooth, dry, concrete roadway, facing uphill or downhill on a 20%
grade. In the emergency mode, the parking brakes must be able to
exert a retarding force equal to 28% of the gross axle rating.
◉ 9. The driver of a truck with hydraulic brakes says the pedal
reserve is too low . Technician A says the brakes could be out of
adjustment Technician B says one brake system may have failed .
Who is right ?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B. Answer: 9. The correct answer is C, both
Technicians are right.
Either condition will cause the driver to notice a low pedal reserve.
◉ 10. The parking brakes fail to apply on a truck with air brakes .
Technician A says this could be caused by low air pressure in the
spring brake chamber . Techni cian B says this could be caused by a
ruptured spring brake diaphragm . Who is right ?
A. Technician A only
B. Technician B only
C. Both A and B