Cooling
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 
slowly.        
      
      
Cooling system radiator