FORD 1998 Expedition - Manual (Page 103)

Using the engine block heater (if equipped)
An engine block heater warms the engine coolant, which improves
starting, warms up the engine faster and allows the heater-defroster
system to respond quickly. Use of an engine block heater is strongly
recommended if you live in a region where temperatures reach -23°C
(-10°F) or below.
For best results, plug the heater in at least three hours before starting
the vehicle. Using the heater for longer than three hours will not harm
the engine, so the heater can be plugged in the night before starting the
vehicle.
To prevent electrical shock, do not use your heater with
ungrounded electrical systems or two-pronged (cheater)
adapters.
Guarding against exhaust fumes
Although odorless and colorless, carbon monoxide is present in exhaust
fumes. Take precautions to avoid its dangerous effects.
If you ever smell exhaust fumes of any kind inside your vehicle,
have your dealer inspect and fix your vehicle immediately. Do
not drive if you smell exhaust fumes. These fumes are harmful and
could kill you.
Have the exhaust and body ventilation systems checked whenever:
• the vehicle is raised for service.
• the sound of the exhaust system changes.
• the vehicle has been damaged in a collision.
Engine exhaust, some of its constituents, and certain vehicle
components contain or emit chemicals known to the State of
California to cause cancer, and birth defects or other reproductive
harm.
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