310T FINAL EXAM 2026/2027 QUESTIONS AND SOLUTIONS
RATED A+
✔✔What is the purpose of residual pressure in a hydraulic brake system?!
To increase the speed of the brake application
To inhibit moisture infiltrating the hydraulic fluid
To increase applied brake pressure
To decrease applied brake pressure - ✔✔To increase the speed of the brake
application
✔✔A driver explains that his low air warning device (light) has activated, but the primary
and secondary pressure gauges indicate full air pressure. What could be the cause?!
A faulty governor setting
An air leak at the supply reservoir
A fault in the air dryer circuit
The low-pressure warning circuit has malfunctioned - ✔✔The low-pressure warning
circuit has malfunctioned
✔✔While troubleshooting an air pressure build up complaint you find no air pressure at
the inlet side of the supply reservoir. What could be the cause?!
A restricted air dryer
Governor setting too high
An empty alcohol evaporator
A defective automatic discharge valve - ✔✔A restricted air dryer
✔✔What would the effect be of a brake drum that has been worn too thin?!
The drum will split and crack
Brakes would pull or grab
Shoes and drum would heat up quickly
S-cam would be unable to rotate - ✔✔Shoes and drum would heat up quickly
✔✔If the air compressor governor failed to cut out, which of the following would result?!
The regulator valve would stop the compressor
The system safety valve would open
The compressor's performance would not be affected
The dash gauges would indicate normal governor cut-out pressure - ✔✔The system
safety valve would open
✔✔What safety precautions must be followed when working on pressurized air brake
components?!
Always wear safety glasses and drain air pressure before dismantling components
Not to worry, pressurized air is not dangerous
Draining air pressure is not required before dismantling components
,Air pressure in a brake system is contained and cannot leak out when dismantled -
✔✔Always wear safety glasses and drain air pressure before dismantling components
✔✔In a B-train combination which of the following relay valves would likely have the
lowest crack pressure?!
The front tractor axle
The rear drive axle
The pup axle
The lead trailer axle - ✔✔The pup axle
✔✔Which of the following would be an output of the ECU (electronic control unit) of an
air brake ABS (anti-lock brake system)?!
The ABS indicator dash light
The exciter ring
The brake treadle valve
The speed sensor - ✔✔The ABS indicator dash light
✔✔Brake wear is uneven on only one side of the shoes. What should be checked?!
Anchor pins and bushings
Improper sized shoes
Worn S-cam bushings
ABS sensor out of adjustment - ✔✔Anchor pins and bushings
✔✔What is the desired air gap between the ABS wheel speed sensor and the exciter
ring?!
1/4" (6.25mm)
3/8" (9.5mm)
Air gap is not critical
As close as possible - ✔✔As close as possible
✔✔What is the proper position of hole(s) on air spring brake chambers?!
At a 90° angle
At a 30° angle
Facing downwards, toward the road
On the top, where it can be accessed - ✔✔Facing downwards, toward the road
✔✔What is the purpose of residual pressure in a hydraulic brake system
To increase speed of a brake application
To inhibit moisture infiltrating the hydraulic system
To increase applied brake pressure
To decrease applied brake pressure - ✔✔To inhibit moisture infiltrating the hydraulic
system
✔✔Air pressure is higher than normal. What is the most likely problem?!
, Un-loader valve is stuck open
Defective governor circuit
Signal from supply tank
Air compressor is over capacity - ✔✔Defective governor circuit
✔✔What is an important requirement when selecting replacement S-cams?!
Identify if a left or right hand S-cam is required
None, as all S-cams are identical
Check for S-cam roller lubrication
Test Rockwell hardness - ✔✔Identify if a left or right hand S-cam is required
✔✔What results when the dash-mounted trailer air supply valve (red) is pulled outward
(closed)?!
Air is directed through the tractor protection valve
The trailer air supply line is fully charged
The tractor parking brakes are applied
The trailer parking brakes are applied - ✔✔The trailer parking brakes are applied
✔✔When servicing an air dryer what also requires replacement?!
Purge valve
Heater element
Desiccant filter
Governor - ✔✔Desiccant filter
✔✔When the inversion valve of an air brake vehicle is in effect, what does it modulate
to slow the vehicle?!
Holds off pressure in the spring brake chamber
Directs air pressure to the service side of the dual chamber
Releases stored air pressure from a separate reservoir
Applies hydraulic pressure to the brakes - ✔✔Holds off pressure in the spring brake
chamber
✔✔What type of signal does an ABS wheel speed sensor provide?!
A digital signal
A sinewave
An AC pulse
A diode - ✔✔An AC pulse
✔✔On an air brake equipped truck that is CMVSS 121 compliant, what is the minimum
air pressure before the low air warning device will activate?!
90 psi
60 psi
100 psi
120 psi - ✔✔60 psi
RATED A+
✔✔What is the purpose of residual pressure in a hydraulic brake system?!
To increase the speed of the brake application
To inhibit moisture infiltrating the hydraulic fluid
To increase applied brake pressure
To decrease applied brake pressure - ✔✔To increase the speed of the brake
application
✔✔A driver explains that his low air warning device (light) has activated, but the primary
and secondary pressure gauges indicate full air pressure. What could be the cause?!
A faulty governor setting
An air leak at the supply reservoir
A fault in the air dryer circuit
The low-pressure warning circuit has malfunctioned - ✔✔The low-pressure warning
circuit has malfunctioned
✔✔While troubleshooting an air pressure build up complaint you find no air pressure at
the inlet side of the supply reservoir. What could be the cause?!
A restricted air dryer
Governor setting too high
An empty alcohol evaporator
A defective automatic discharge valve - ✔✔A restricted air dryer
✔✔What would the effect be of a brake drum that has been worn too thin?!
The drum will split and crack
Brakes would pull or grab
Shoes and drum would heat up quickly
S-cam would be unable to rotate - ✔✔Shoes and drum would heat up quickly
✔✔If the air compressor governor failed to cut out, which of the following would result?!
The regulator valve would stop the compressor
The system safety valve would open
The compressor's performance would not be affected
The dash gauges would indicate normal governor cut-out pressure - ✔✔The system
safety valve would open
✔✔What safety precautions must be followed when working on pressurized air brake
components?!
Always wear safety glasses and drain air pressure before dismantling components
Not to worry, pressurized air is not dangerous
Draining air pressure is not required before dismantling components
,Air pressure in a brake system is contained and cannot leak out when dismantled -
✔✔Always wear safety glasses and drain air pressure before dismantling components
✔✔In a B-train combination which of the following relay valves would likely have the
lowest crack pressure?!
The front tractor axle
The rear drive axle
The pup axle
The lead trailer axle - ✔✔The pup axle
✔✔Which of the following would be an output of the ECU (electronic control unit) of an
air brake ABS (anti-lock brake system)?!
The ABS indicator dash light
The exciter ring
The brake treadle valve
The speed sensor - ✔✔The ABS indicator dash light
✔✔Brake wear is uneven on only one side of the shoes. What should be checked?!
Anchor pins and bushings
Improper sized shoes
Worn S-cam bushings
ABS sensor out of adjustment - ✔✔Anchor pins and bushings
✔✔What is the desired air gap between the ABS wheel speed sensor and the exciter
ring?!
1/4" (6.25mm)
3/8" (9.5mm)
Air gap is not critical
As close as possible - ✔✔As close as possible
✔✔What is the proper position of hole(s) on air spring brake chambers?!
At a 90° angle
At a 30° angle
Facing downwards, toward the road
On the top, where it can be accessed - ✔✔Facing downwards, toward the road
✔✔What is the purpose of residual pressure in a hydraulic brake system
To increase speed of a brake application
To inhibit moisture infiltrating the hydraulic system
To increase applied brake pressure
To decrease applied brake pressure - ✔✔To inhibit moisture infiltrating the hydraulic
system
✔✔Air pressure is higher than normal. What is the most likely problem?!
, Un-loader valve is stuck open
Defective governor circuit
Signal from supply tank
Air compressor is over capacity - ✔✔Defective governor circuit
✔✔What is an important requirement when selecting replacement S-cams?!
Identify if a left or right hand S-cam is required
None, as all S-cams are identical
Check for S-cam roller lubrication
Test Rockwell hardness - ✔✔Identify if a left or right hand S-cam is required
✔✔What results when the dash-mounted trailer air supply valve (red) is pulled outward
(closed)?!
Air is directed through the tractor protection valve
The trailer air supply line is fully charged
The tractor parking brakes are applied
The trailer parking brakes are applied - ✔✔The trailer parking brakes are applied
✔✔When servicing an air dryer what also requires replacement?!
Purge valve
Heater element
Desiccant filter
Governor - ✔✔Desiccant filter
✔✔When the inversion valve of an air brake vehicle is in effect, what does it modulate
to slow the vehicle?!
Holds off pressure in the spring brake chamber
Directs air pressure to the service side of the dual chamber
Releases stored air pressure from a separate reservoir
Applies hydraulic pressure to the brakes - ✔✔Holds off pressure in the spring brake
chamber
✔✔What type of signal does an ABS wheel speed sensor provide?!
A digital signal
A sinewave
An AC pulse
A diode - ✔✔An AC pulse
✔✔On an air brake equipped truck that is CMVSS 121 compliant, what is the minimum
air pressure before the low air warning device will activate?!
90 psi
60 psi
100 psi
120 psi - ✔✔60 psi
