T4 ASE BRAKES (MEDIUM/HEAVY DUTY
BRAKES) EXAM 2024/25!!
What are symptoms of defective supply system components? - ANSWER - Brakes not applying/releasing
properly and grabbing or dragging
How much of a difference in psi air delivery between axles can cause instability and premature wear? -
ANSWER - 4-psi
If all-around braking performance is poor or if the system is not building up enough air pressure, look for
signs such as: - ANSWER - A clogged air compressor filter, slipping belt, air leaks, restricted lines, a
defective governor, or even a malfunctioning air compressor
What is an air brake governor? - ANSWER - An air brake governor controls the compressor. It maintains
reservoir air pressure between a predetermined min. and max. air pressure.
If system pressure is too high suspect a: - ANSWER - Defective governor or reservoir safety valve.
If a governor's cut-out pressure is too high, it can cause: - ANSWER - Over-pressurization
A faulty reservoir safety valve: - ANSWER - May not be allowing excessive air pressure to be purged from
the air tanks
When releasing the service brakes and timing the air pressure drop, the loss rate should be less than
___psi/minute for straight trucks and less than ___psi/minute for combination vehicles. - ANSWER - Less
than 2psi/minute for straight trucks and less than 3psi/minute for combination vehicles.
When applying the service brakes to at least 90 psi and timing the air pressure drop, the loss rate should
be less than ___psi/minute for straight trucks and less than ___psi/minute for combination vehicles. -
ANSWER - Less than 3psi/minute for straight trucks and less than 4psi/minute for combination vehicles.
,Trucks with air brakes come equipped with pressure gauges mounted on the dash. The gauges will
indicate: - ANSWER - How much air pressure is in the system at any given time
When system pressures fall below ___ psi, either a warning light will illuminate, or a buzzer will sound. -
ANSWER - 60 psi
Some systems include a _____ _______ gauge, which can inform the driver of specific pressure when
the brakes are applied. - ANSWER - Separate application gauge
Dash air pressure gauges operate on the principle of changing an: - ANSWER - Air brake pressure signal
into an electronic voltage signal
An element inside an ___ ________ __________ responds to air pressure increase or decrease, the
__________ converts that pressure differentiation into a voltage signal, which is displayed in a
proportionate reading in the dash gauge. - ANSWER - Air pressure transducer; transducer
To check the transducer and gauge assembly, make sure the air supply value and transducer output
voltage are within _______ - ANSWER - The manufacturer's specifications
If the transducer voltage output is not within normal readings, suspect a - ANSWER - Defective
transducer
If the transducer voltage output is within normal readings, suspect a - ANSWER - Defective gauge
A defective ________ device will fail to signal the driver of diminished air pressure in the brake system. -
ANSWER - Low-pressure warning device
The low-pressure warning indicator is installed on the ______ reservoir, and notifies the operator of
____________. - ANSWER - Primary reservoir; system air depletion
To check the operation of the low-pressure warning indicator, completely ______ the air brake system. -
ANSWER - Depressurize
, If at 60 psi the low-pressure indicator signals do not operate, check for ______ at the warning device. If
the circuit is open, suspect a ________. - ANSWER - Voltage; defective low-pressure warning device
To replace the low-pressure warning device: - ANSWER - Completely depressurize the air brake system,
remove the air lines, and unscrew from the primary reservoir.
The ______ reservoir or 'wet tank' is the one closest to the compressor - ANSWER - Supply reservoir
When the brake pedal is depressed, air flows from the primary reservoir, through the primary section of
the foot valve, and out to the _______________. - ANSWER - Rear foundation brakes
When the brake pedal is depressed, air flows from the secondary reservoir, through the secondary
section of the foot valve, and out to the _______________. - ANSWER - Front foundation brakes
When inspecting the air tank reservoirs, note any damage that may have been cause by ________. -
ANSWER - Road debris
When inspecting air reservoir mounting, take into consideration adequate clearance for other
components such as __________ and ________. - ANSWER - Power take off assemblies and brake lines
A malfunctioning air compressor can develop air leaks and pass oil into the brake system, which in turn
will cause ____________, _______, ________. - ANSWER - Poor stopping, grabbing, or dragging
Although there are many other components in the air brake system, the one that bears the heaviest
burden is the _____________. - ANSWER - Air compressor
A ______-cylinder or _______-cylinder compressor is used for most truck applications. However, ______
and ______-cylinder air compressors are available for applications where high air volume is in demand. -
ANSWER - Single-cylinder; two-cylinder; three and four-cylinder
Compressors can be _______ cooled, ______ cooled, or both. - ANSWER - Liquid cooled, air cooled
BRAKES) EXAM 2024/25!!
What are symptoms of defective supply system components? - ANSWER - Brakes not applying/releasing
properly and grabbing or dragging
How much of a difference in psi air delivery between axles can cause instability and premature wear? -
ANSWER - 4-psi
If all-around braking performance is poor or if the system is not building up enough air pressure, look for
signs such as: - ANSWER - A clogged air compressor filter, slipping belt, air leaks, restricted lines, a
defective governor, or even a malfunctioning air compressor
What is an air brake governor? - ANSWER - An air brake governor controls the compressor. It maintains
reservoir air pressure between a predetermined min. and max. air pressure.
If system pressure is too high suspect a: - ANSWER - Defective governor or reservoir safety valve.
If a governor's cut-out pressure is too high, it can cause: - ANSWER - Over-pressurization
A faulty reservoir safety valve: - ANSWER - May not be allowing excessive air pressure to be purged from
the air tanks
When releasing the service brakes and timing the air pressure drop, the loss rate should be less than
___psi/minute for straight trucks and less than ___psi/minute for combination vehicles. - ANSWER - Less
than 2psi/minute for straight trucks and less than 3psi/minute for combination vehicles.
When applying the service brakes to at least 90 psi and timing the air pressure drop, the loss rate should
be less than ___psi/minute for straight trucks and less than ___psi/minute for combination vehicles. -
ANSWER - Less than 3psi/minute for straight trucks and less than 4psi/minute for combination vehicles.
,Trucks with air brakes come equipped with pressure gauges mounted on the dash. The gauges will
indicate: - ANSWER - How much air pressure is in the system at any given time
When system pressures fall below ___ psi, either a warning light will illuminate, or a buzzer will sound. -
ANSWER - 60 psi
Some systems include a _____ _______ gauge, which can inform the driver of specific pressure when
the brakes are applied. - ANSWER - Separate application gauge
Dash air pressure gauges operate on the principle of changing an: - ANSWER - Air brake pressure signal
into an electronic voltage signal
An element inside an ___ ________ __________ responds to air pressure increase or decrease, the
__________ converts that pressure differentiation into a voltage signal, which is displayed in a
proportionate reading in the dash gauge. - ANSWER - Air pressure transducer; transducer
To check the transducer and gauge assembly, make sure the air supply value and transducer output
voltage are within _______ - ANSWER - The manufacturer's specifications
If the transducer voltage output is not within normal readings, suspect a - ANSWER - Defective
transducer
If the transducer voltage output is within normal readings, suspect a - ANSWER - Defective gauge
A defective ________ device will fail to signal the driver of diminished air pressure in the brake system. -
ANSWER - Low-pressure warning device
The low-pressure warning indicator is installed on the ______ reservoir, and notifies the operator of
____________. - ANSWER - Primary reservoir; system air depletion
To check the operation of the low-pressure warning indicator, completely ______ the air brake system. -
ANSWER - Depressurize
, If at 60 psi the low-pressure indicator signals do not operate, check for ______ at the warning device. If
the circuit is open, suspect a ________. - ANSWER - Voltage; defective low-pressure warning device
To replace the low-pressure warning device: - ANSWER - Completely depressurize the air brake system,
remove the air lines, and unscrew from the primary reservoir.
The ______ reservoir or 'wet tank' is the one closest to the compressor - ANSWER - Supply reservoir
When the brake pedal is depressed, air flows from the primary reservoir, through the primary section of
the foot valve, and out to the _______________. - ANSWER - Rear foundation brakes
When the brake pedal is depressed, air flows from the secondary reservoir, through the secondary
section of the foot valve, and out to the _______________. - ANSWER - Front foundation brakes
When inspecting the air tank reservoirs, note any damage that may have been cause by ________. -
ANSWER - Road debris
When inspecting air reservoir mounting, take into consideration adequate clearance for other
components such as __________ and ________. - ANSWER - Power take off assemblies and brake lines
A malfunctioning air compressor can develop air leaks and pass oil into the brake system, which in turn
will cause ____________, _______, ________. - ANSWER - Poor stopping, grabbing, or dragging
Although there are many other components in the air brake system, the one that bears the heaviest
burden is the _____________. - ANSWER - Air compressor
A ______-cylinder or _______-cylinder compressor is used for most truck applications. However, ______
and ______-cylinder air compressors are available for applications where high air volume is in demand. -
ANSWER - Single-cylinder; two-cylinder; three and four-cylinder
Compressors can be _______ cooled, ______ cooled, or both. - ANSWER - Liquid cooled, air cooled
