The air system provides the air supply to operate the
and the primary supply reservoir.
service brakes, the differential locks, the engine
governor is on an unload cycle, the air dryer
throttle, and the rear steering lock. The air system
functions to remove water and oil vapor from the air.
also provides air to the trailer air couplings, the rear
An alcohol evaporator is installed below the primary
air supply coupling, and the tire inflation couplings.
supply reservoir and connected between the
The air system is pressurized by an air compressor
secondary and auxiliary air reservoirs.
mounted on the engine. The air pressure generated
by the compressor is stored in three air reservoirs
passes through the evaporator, alcohol is evaporated
mounted to the carrier frame. From these reservoirs,
into the air to act as antifreeze to keep any moisture
air is provided for operation of the above mentioned
in the air from freezing and causing air actuated
components in auxiliary air circuit from locking up.
A dual air pressure gauge is provided in each cab to
The air system is a split system wherein the primary
monitor air pressure in the system. The red arrow
and secondary systems are isolated from each other
indicates primary air pressure (primary supply
under normal operation. Therefore, in the event of
reservoir), while the green arrow indicates secondary
the failure of one system, air is retained in the other
pressure (secondary and auxiliary air reservoirs).
and, by means of the pressure protection valves, and
check valves, a reserve of air pressure remains to
An air dryer is installed beside the primary supply
operate the brakes through normal use of the brake
reservoir, and is connected between the compressor
pedal. Any unusual loss of pressure should be
investigated immediately and corrected, so as to
restore the full back-up capability of the system.
All connecting lines of the air system are either tubing
or flexible hoses. All tubing in the system is nylon,
If a leak is suspected in the air system, shut down
except that from the compressor to the air dryer.
the engine and record the pressure readings of the
green and red arrow in the air pressure gauge on the
front console. A loss of 6 psi (41.37 kPa) or less
within a 30 minute time interval is usually considered
Before removing or disconnecting any
component or line of the air system,
If a leak is detected and not obvious, the leaking
ensure that all air pressure in both
valve, fitting, or reservoir may be isolated by wetting
systems has been depleted.
the suspected area with a concentrated liquid soap
solution and observing for bubbles.
Do not allow the nylon tubing to be
exposed to flames or excessive heat. If
Before attempting to remove any
any white shows through the outside
components for leak repair, ensure that
covering, that section of the line should
all air pressure in both air systems has
be replaced, and action taken to
eliminate the cause of the chafing or