Operating the Engine Operating Instructions
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Medium Duty (R10/06)
WARNING! Never idle your vehicle for prolonged
periods of time if you sense that exhaust fumes
are entering the cab. Investigate the cause of the
fumes and correct it as soon as possible. If the
vehicle must be driven under these conditions,
drive only with the windows slightly open. Fail-
ure to repair the source of the exhaust fumes
may lead to personal harm.
Idling the Engine
Under most circumstances, continuous idling of your engine
merely wastes fuel. In severe Arctic weather conditions, how-
ever, you may need longer idling to be sure all parts of your
engine are fully lubricated.
CAUTION: Do not allow your engine to idle, at
low rpm (400–600 rpm), longer than five minutes.
Long periods of idling after the engine has
reached operating temperatures can decrease
engine temperature and cause gummed piston
rings, clogged injectors, and possible engine
damage from lack of lubrication. The normal torsional
vibrations generated can also cause transmission wear.
• During the time it takes you to drink a cup of coffee, your
engine can cool as much as 60° F (33° C) below normal
operating temperature. To keep the engine warm during
a short break, turn it off. Do not allow your engine to idle
longer than five minutes.
Engine Fan Switch (Option)
Your Medium Duty may have an engine fan switch installed
as an option. The switch, which is mounted on the accessory
switch panel, allows you to control the engine fan manually or
automatically.
• With the ignition key switch ON and the fan switch in the
ON position, the engine fan will be on regardless of
engine temperature.
• With the engine fan switch in the AUTOMATIC position,
the engine fan will automatically turn on when the engine
coolant reaches a temperature of about 200°F (93°C)
