Ford 2002 F650 Owner's Manual page 195

If you drive in extremely hot climates:
• It is still necessary to maintain the coolant concentration
above 40%.
• NEVER decrease the coolant concentration below 40%.
• Decreased engine coolant concentrations below 40% will
decrease the corrosion protection characteristics of the engine
coolant and may cause engine damage.
• Decreased engine coolant concentrations below 40% will
decrease the freeze protection characteristics of the engine
coolant and may cause engine damage.
• Refer to the chart on the coolant container to ensure the
coolant concentration in your vehicle will provide adequate
protection at the temperatures in which you drive.
Vehicles driven year-round in non-extreme climates should use a 50/50
mixture of engine coolant and distilled water for optimum cooling system
and engine protection.
Coolant conditioner (liquid)
For engines filled with green-colored Motorcraft Premium Engine
Coolant, a supplemental coolant additive FW-16 meeting Ford
specification ESN-M99B169–A has been added to the coolant in this
engine.
This additive aids in the prevention of rust and scale buildup on the
internal parts of the cooling system. Prevention of rust and scale buildup
allows for proper dissipation of heat generated by combustion.
See the "scheduled maintenance guide" for recommended intervals.
Fan clutches
Your vehicle's cooling system is equipped with a viscous variable speed
fan clutch.
• The fan clutch helps control cooling, increase performance, improve
fuel economy and reduce noise.
• The fan clutch is controlled by bimetallic spring sensors. Do not
tamper with these sensors as this may change their calibration or keep
the fan clutch from operating at all.
Maintenance and Specifications
195