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How Does it Work /
Radiator Cooling
System
How an Engine Cooling Systems Works
Inside your car's engine, thousands of controlled explosions called
combustion events caused by igniting fuel / air mixture inside the engine.
Spark
plugs are used to ignite the fuel / air mixture contained in the cylinders.
These explosions are converted into power through the engine while producing a large
amount of heat. These high temperatures are controlled with the help of the cooling
system. A cooling system consists of a water pump, thermostat, radiator hose, hose
clamps, radiator, radiator cap and coolant.
Typical Engine Cooling System
The engine's combustion chamber reaches up to a temperature of four thousand
five hundred degrees Fahrenheit. About thirty percent of the fuel is converted into
actual power, and about seventy percent is spent into heat. A cooling system protects
an engine from damage by transferring heat to the atmosphere by using the
radiator. A correct operating temperature is critical for the proper function
of the engine. The thermostat controls when coolant is allowed to flow into the
radiator and back into the engine. Manufacturers have found that a 195 degree thermostat
is optimum for efficiency. Below this threshold the catalytic converter will not
work to capacity and will produce increased emissions. Coolant is pumped through
the engine block by the water pump where it passes into the
radiator. Automatic transmission vehicles utilize a fluid cooler inside the
engine coolant radiator. This cooler is use to cool the transmission fluid that
has been heated from normal usage.
Engine coolant is used to transfer heat from the
engine
to the
radiator by the
cooling
system. The radiator remove heat from the coolant by forcing air through
the radiator fins. Without coolant your engine will over heat and if left
unattended sever engine damage will occur. Coolant colors can vary from green,
orange, blue and yellow each having there own protective properties.
(note: coolant and antifreeze refer to the same product, in below freezing,
coolant lowers the freeze point hence the name anti-freeze and in warm weather
coolant helps raise the boiling point, "coolant")
Red and Green Engine Coolant
In the beginning, water was used for cooling systems as it is the most efficient
fluid to absorb and dissipate heat. The disadvantage of using water is that it freezes
and will rust. Then water was mixed with ethylene glycol which worked as an antifreeze
element. Not only does the freezing point improve so does the boiling point by adding
ethylene glycol. Ethylene glycol can be heated up to 250�F before
becoming ineffective. The cooling system is pressurized to 18 psi. to increase coolant
boiling point which adds 9 degrees Fahrenheit to the boiling point of the coolant.
Coolant is also used to avoid corrosion. An engine
thermostat is designed to stop the flow of coolant from the engine to the
radiator. This temperature sensitive valve is designed to open when the
engine has reached operation temperature (190�-198�
F). The operating temperature of 190�-210�
F. which is used to help facilitate fuel combustion. When a
thermostat fails it will either stop the coolant flow at operating
temperature "stick closed" or fail to stop the coolant flow causing the
engine to run colder longer then necessary. If the thermostat fails "open"
it will cause the coolant to continuously flow through the engine creating a
diagnostic trouble code (check
engine light) will be set. When a thermostat sticks it will cause the
engine to overheat quickly, usually with in 5 to 15 minutes of operation. To
check for either of these conditions drain coolant and remove thermostat,
(under the thermostat housing) if you are unsure of the location of the
thermostat on your engine consult a
car repair
manual. Once you have removed the thermostat inspect the condition of
the main body check for any cranks or broken pieces and check the valve to
make sure it is closed. If the valve is open the thermostat has failed and
needs to be replaced. To check the operation of the thermostat prepare a pot
of water on the stove deep enough to cover the thermostat completely.
Install the thermostat in the pot of water, turn the stove on a medium/high
flame, the thermostat should open right before the water comes to a boil. If
the water has boiled and the thermostat valve is still closed the thermostat
has failed and needs to be placed.
Engine Thermostat
The engine cooling fan system in your car is designed to move air
through the radiator when the vehicle is at slower speeds. This air flow
removes heat from the coolant created by the engine using the radiator as a
conductor. Most radiator cooling fans are powered by the engine or by
electricity. When a cooling fans fails it causes the coolant to retain heat,
forcing the engine to run hot and eventually over heat. A cooling fan that
is powered by the motor is engaged and disengage from operation by a temperature
controlled fan clutch. This fan clutch is constructed using a silicon grease and
temperature sensitive coil spring that expands and contracts with heat. As the
spring absorbs heat it expands engaging the clutch fan utilizing engine power to
drive the fan. A clutch fan can fail one of two ways, it can either locking the
fan to the clutch causing poor mileage and a wirrrring sound, like an airplane
is taking off next to you. Or the silicon grease can start to leak causing the
fan clutch not to lock up allowing the fan to "freewheel", failing to pull air
through the radiator. To check for this condition the engine must be off, then
inspect the fan clutch for leakage at the front or rear of the unit (input shaft
and temperature controlled expansion spring). If leakage is observed the fan
clutch has failed and needs replacing. Next, take the fan blade and turn it, the
fan blade should free wheel, if you can not turn the fan blade the clutch has
locked up and needs to be replaced.
Engine Fan Clutch (fan blade not attached)
To inspect an electric motor cooling fan start with key off, engine off, next
spin the fan blade it should "freewheel" if the fan motor does not spin it has
failed and needs to be replaced. If the fan motor "freewheels" the electrical
system that operates the fan needs to be tested. Start the engine and turn the
air conditioner to the coolest setting, if your car does not have an air
conditioner skip this step. Within three minuets of the car air conditioner
operating the cooling fan should activate, if not the fan motor
fuse must be checked
first, if the fuse condition is ok the remainder of the electrical system must
be checked. To further troubleshoot this problem a wiring schematic is needed
which is located in a
car repair
manual. Use the wiring schematic to trace the circuit through the fuse and
relay components, if everything tests ok the fan motor has failed and needs to
be replaced.
Radiator Cooling Fan
The water pump is driven by a belt, powered by the engine which circulates coolant
when the engine is running. This pump utilizes centrifugal force to pull the coolant
from the block to the radiator. Most radiators
are made of an aluminum core and plastic side tanks. Aluminum cooling fins are fastened
to flattened aluminum tubes. These aluminum tubes direct the flow of coolant through the radiator. The amount
of heat transferred from the coolant depends on the surface area of the core. The
radiator cap acts like a pressure release valve, as the pressure increases do to
heat, the cap allows the excess coolant to enter the reservoir. Then, when the engine
has cooled the coolant will return to the radiator.
Basic Checks
Low levels of coolant can lead to problems related to engine overheating. Always
maintain proper levels of coolant in the overflow coolant reservoir tank. ONLY!
check the radiator when the engine is cold. Only add antifreeze and reinstall the
cap properly. Always drain and refill your
cooling system regularly.
How Does it Work
/ Radiator Cooling
System
Check Manufacturer Specific Radiator
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