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Engine Cooling System
- When the engine is running, it naturally
generates heat. That heat must be managed to avoid
damaging the engine. Some of this heat must be
removed from the engine and dissipated or
transferred.
- There are many parts to the engine cooling
system.
- The engine has many passages that surround the
cylinders. These passages are filled with antifreeze
or coolant (These terms are used inter-changeably).
- When the engine is started, the water pump
begins to circulate that coolant through the engine.
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Once
the engine reaches between 180 and 195 degrees
Fahrenheit, the thermostat opens and allows this
coolant to circulate through the radiator.
- Air moves through the radiator (either from the
car moving, or when the car is stopped, from the fan
used to pull air though the radiator). The heat
from the hot coolant is transferred to the air.
- The water pump also circulates hot coolant to
the heater core under the dash where it provides
heat for inside the passenger compartment.
- Coolant moves through the cooling system using
metal tubes and rubber hoses
- Coolant/antifreeze wears out, becomes caustic,
and begins to attack parts of the cooling system.
- Without going into detail, it is important to
flush and change the coolant every two to three
years.
Air Conditioning System
- The sole purpose of the AC system is to keep the
vehicle passengers cool.
-
While
it depends on the engine cooling system to
help eliminate or pull heat from inside the
passenger compartment, it is a completely
separate system from the engine cooling system.
-
Instead
of coolant or antifreeze, the AC system uses and
circulates refrigerant (sometimes called Freon)
through the system.
- Older cars used something called R12
refrigerant. But R12 was found to cause holes in
the Earth’s ozone layer.
- Next, in the mid-1990’s, R12 was replaced by
R134a refrigerant. But since then, R134a has
been found to promote green house gases which
cause global warming.
- Coming soon to vehicles near you, new
refrigerants!!!!
- Back to how the system works.
- The AC compressor pumps refrigerant through
hoses and lines.
- The refrigerant enters a unit under the
dashboard called an evaporator.
- The blower fan under the dash circulates hot air
from inside the passenger compartment, through the
evaporator. The refrigerant in the evaporator
absorbs this heat and that heated refrigerant is
pumped (by the compressor) to a unit called the
condenser located at the front of the car in front
of the engine cooling system radiator.
- Just like the engine cooling system radiator,
the AC condenser transfers this heat to the air.
- Then the “cooled” refrigerant is circulated back
toward the passenger compartment where it passes
through a filter/drier (sometimes called an
accumulator) and a metering valve (called an orifice
tube or expansion valves) and returns to the
evaporator where the whole cycle starts all over
again.
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If
the engine cooling system is not working properly
it can seriously impede the operation of the AC
system (even to the point of destroying the AC
system).
- For more information on the engine cooling
system and AC system, see questions below.
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