Lesson 2/Learning Event 3
Check to see that the governor operates when the pressure
reaches about 105 PSI. (If the governor does not stop the
pressure from building up over 105 to 120 PSI, the engine must
be shut off and the system repaired.)
Operate the brake pedal several times. Check the action of
the pedal by its feel. You should be able to tell if the
brakes are applying.
Pump the brakes until the air pressure drops to about 80 to
105 PSI. At this time the governor should start the
compressor again and the pressure should build back up to
about 105 to 120 PSI and stay there.
When the pressure has reached 105 to 120 PSI, turn the engine
in one minute so that you can notice it on the gage, it
indicates there is a leak in the system that must be
The road test part of the inspection is made to determine how well
the working parts of the brake system are operating. When making a
road test, the vehicle trailer should be connected to the truck so
that the entire braking system can be tested. Test the operation of
the brakes several times. This should be done at various speeds from
20 to 40 MPH. Try slowing the vehicle and bringing it to a complete
stop. Check to see if
Excessive pressure is required on the brake pedal to stop the
The brake pedal must be pressed down near the floorboard
before the brakes hold.
The vehicle pulls to one side when braking.
The vehicle comes up to the proper speed.
One or more brakes lock when braking rapidly.
There is any unusual noise or chatter when the brakes are