Navistar WorkStar Series, Operator'S Manual

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Operation
• Clutched Air Compressor: This high-capacity, two
cylinder, air compressor is periodically engaged by using
an on-off clutch. It works in conjunction with air governor
and air dryer to pump air to the air dryer and air tanks.
When additional compressed air is not needed, the clutch
is disengaged, compressor speed goes to zero, and all
air pumping ceases. This system provides relatively low
cylinder temperatures and sound verses other compressors
during the unloaded cycle. It is used to promote maximum
fuel economy by eliminating pumping energy loss during
the unloaded cycle.
As the compressor reaches approximately 120 psi (827 kPa),
the air governor will, through various methods stop the air
compressor from pumping pressurized air to the air system.
When the air pressure reaches approximately 105 psi (724
kPa), the governor signals the air compressor to resume
pumping pressurized air to the air system.
During normal
engine operation, this cycle will be evident by the fluctuation of
the primary air tank pressure gauge.
Cooling System
WARNING
To prevent personal injury or death from hot
coolant
or steam, use only the following
procedure to remove the pressure cap from
the deaeration tank.
Allow the engine to cool
first. Wrap a thick, heavy cloth around the
cap. Depending on the type of cap, push down,
loosen cap slowly to its first notch position, or
unscrew cap slowly; then pause a moment to
allow pressure to release through the overflow
tube. After the pressure has been released, the
pressure cap may be removed.
WARNING
Exercise care when working on vehicles with
running engines that are equipped with an
automatic fan clutch.
The fan engages when
engine coolant reaches a predetermined
temperature or the refrigerant pressure (if
equipped with air conditioning) reaches a
predetermined setting. The fan will start with
no advance warning. Failure to observe these
precautions could result in vehicle damage,
personal injury, or death.
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