Ford F-650 Owner's Manual page 198

Maintenance and Specifications
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.
Fan clutches
Your vehicle's cooling system is equipped with a viscous fan clutch
which:
• Helps control cooling, increase performance, improve fuel economy
and reduce noise.
• 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.
WARNING: Stay clear of the fan/fan area while the engine is
running or possible personal injury may occur.
ENGINE COOLANT (GAS ENGINE ONLY)
Checking engine coolant
The concentration and level of engine coolant should be checked at the
intervals listed in your scheduled maintenance information. The coolant
concentration should be maintained at 50/50 coolant and distilled water.
For best results, coolant concentration should be tested with a
refractometer such as Rotunda tool 300-ROB75240E available from your
dealer. Ford does not recommend the use of hydrometers or coolant test
strips for measuring coolant concentration. The level of coolant should
be maintained at the FULL COLD level or within the COLD FILL RANGE
in the coolant reservoir. If the level falls below, add coolant per the
instructions in the Adding engine coolant section.
Your vehicle was factory-filled with a 50/50 engine coolant and water
concentration. If the concentration of coolant falls below 40% or above
60%, the engine parts could become damaged or not work properly. A
50/50 mixture of coolant and water provides the following:
• Improved freeze protection.
• Improved boiling protection.
• Protection against rust and other forms of corrosion.
• Proper function of calibrated gauges.
When the engine is cold, check the level of the engine coolant in the
reservoir.
198
2012 F-650/750 (f67)
Supplement, 2nd Printing
USA (fus)