Combustion 101

Within the walls of the engine block and surrounding
the cylinders are small passages through which water is
pumped through.  The water absorbs the heat from the
engine block and is pumped outside to a radiator.  A
radiator is made up of several small flat tubes covered
with tiny fins, and exposed to outside air flow.  Hot
water is pumped into the tubes of the radiator, and then
the air passing around the tubes cools the water.  This
process is made more efficient with the tiny fins, which
air.  Basically creating more places for the heat to
escape.  This cooled water can now be pumped back
into the engine block, to absorb more engine heat.  

To improve the cooling process, fans are added to the
radiator to increase the airflow over the cooling tubes.   
Fans turned by the rotation of the engine itself, spin
constantly pulling cold air through the radiator.  Electric
fans are often used in place or in addition to the engine
powered fans.  Independent electric fans can spin
quickly even to cool the engine even when the engine
spins slowly-and the car is not moving. This is the case
in slow moving traffic.  The electric fan turns off when
the car is moving faster and enough air is flowing
through the radiator to cool the water.  

Another improvement to the cooling system is the
thermostat valve.  This valve isolates the radiator from
the water flowing throughout the engine block.  When
the water temperature gets hot enough, the valve opens
releasing cold radiator water into the hot engine block.  
There are two benefits of a thermostat valve:  the
engine has a chance to warm up to its operating
temperature (at which combustion is most efficient)
without interference from cooled water from the
radiator.  Ideal water temperatures are between about
150 and 250 degrees Fahrenheit.  These vary based on
the engine design.  If the engine was too cold, its
components could shrink and gaps could occur at joints
and seals causing leaks.  With the engine warmed, the
natural expansion of the metal pushes seals and gaps
closed.  Simply put, engine parts fit together better
when they are warm.    

Second when the radiator is isolated by the thermostat
valve, the water within it has time to cool to a lower
temperature (heat transfer takes time) so it can cool
more effectively when the engine does get too hot.  
Once the engine water reaches the thermostatic valve
activation temperature, the valve opens allowing rapid
cooling to occur.  When the water temperature cools
back below the thermostatic valves activation
temperature it closes, letting the radiator water cool
Cooling system radiator
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