Step by step instructions on how an internal combustion engine cooling system
There are thousands of controlled explosions called combustion events which are
caused by igniting a fuel air mixture inside the combustion chamber. These explosions
are converted into thrust throughout the engine while producing an amount of heat.
High temperatures would make the engine overheat if not for the cooling system.
Engine Cooling System
. The cooling system is a pressurized, sealed circulation system that
consists of seven major components:
Fluid is used to dissipate heat away from the engine's block and cylinder heads.
Most engine's have an optimum operating temperature of around 200 degrees Fahrenheit
or about 93 degrees Celsius.
This temperature is maintained using a thermostat which is designed to allow
coolant to flow throughout the system. Normal water boils at 212 degrees Fahrenheit,
or 100 degrees Celsius, and freezes at 0 Celsius or 32 degrees Fahrenheit, where
as coolant boils at 223 degrees and freezes well below 32 degrees. Coolant is also
used to avoid corrosion which can damage vital engine parts such as gaskets and
The cooling system is held under pressure while under operation, between 13-15
psi (pounds per square inch.)
This additional pressure helps the coolant gain additional boiling point temperatures
at a rate of one degree for every two pounds of pressure. For example; when a cooling
system is held at 18 pounds of pressure it raises the boiling point by 9 degrees.
Always check the radiator coolant level when the engine is cold. Visit -
- Coolant leak
Step 2 - Water Pump
The water pump is a mechanical pump that circulates the engine coolant throughout
the radiator and into the engine block and cylinder head(s) which is driven by an
serpentine or timing belt or by the timing chain. When a water pump fails it can
produce a squeaking or rattling sound.
Also, a water pump can leak engine coolant through a relief port that allows
coolant to pass when the shaft seal fails. This port is created so engine coolant
will not contaminate the shaft bearings causing a worse problem.
If a failing or failed water pump is allowed to operate it can cause the engine
to overheat or completely fail. A water pump is comprised of a main housing body,
flange, main shaft, bearings, impeller, seals and a gasket to seal in against the
When engine RPM increase so does the water pump flow rate. A water pump will
typical last between 50,000 and 80,000 miles. When replacing a water pump always
insist on high quality replacement parts to avoid a premature failure. Visit -
Water Pump (Serpentine Belt Removed)
Step 3 - Cooling Thermostat
A thermostat is a temperature sensitive device located in the thermostat housing.
The thermostat housing is located at the engine, in either the upper or lower hose
connections. This thermostat restricts the coolant from the radiator until the engine
has reach operating temperature which is about 195°.
This allows for the engine to be run at specific temperatures to optimize the
performance and emissions levels. When a thermostat sticks closed, it will cause
the engine to overheat quickly, usually within 5 to 15 minutes of engine operation.
Visit - Thermostat
Step 4 - Radiator
Engine Thermostat and Housing
A radiator is used to transfer heat from the engine coolant to the outside atmosphere
via the cooling fins of the radiator. When air is forced through these fins either
with the assistance of the cooling fan or the vehicles forward motion it lowers
the temperature of the coolant which is then moved to the engine to re-start the
cycle of heating and cooling. The amount of heat transferred from the coolant depends
on the surface area of the radiator core.
Automatic transmission vehicles, utilize a fluid cooler inside the radiator.
The radiator cap acts like a pressure release valve, as the pressure increases due
to heat, the cap allows the excess coolant to enter the reservoir. Then, when the
engine has cooled, coolant is returned to the radiator through suction. Most radiators
are made of an aluminum core, and plastic side tanks. Visit -
Step 5 - Cooling Fan
The cooling fan is located directly behind the radiator and is used to pull air
through the radiator at lower vehicle speeds to keep the engine from overheating.
Cooling fans can either be mechanical which are belt driven, or electric, mounted
on the radiator and temperature or utility controlled. Visit -
A radiator cooling fan is powered by either the engine, or by an electric motor.
When a cooling fan fails, it causes the coolant to retain heat, forcing the engine
to run hot and eventually overheat. Cooling fans that is powered by the engine are
engaged and disengaged by operating temperature which is controlled by a fan clutch.
Visit - Fan clutch
Radiator Cooling Fans
- Coolant Hoses
Engine coolant is transferred to various sections of the cooling system via cooling
hoses. These hoses are double-walled nylon reinforced pre-molded units capable of
withstanding high temperatures while enduring engine vibrations. Part of a routine
maintenance schedule should be the inspection of the cooling system hoses.
When inspecting these hoses there are a few things to look for that would warrant
replacement: oil saturation, cracks, abrasions, seepage and clamp tightness. Visit
- Coolant leaks
Visit - Radiator
Step 7 - Serpentine Belt
A serpentine belt is used to transfer energy from the engine to the cooling fan
on clutch fan style of cooling fans. This belt must be maintained for the fan to
operate properly, usually when the belt fails the battery warning light will illuminate.
Visit - Serpentine
Step 8 - Oil Cooler
An engine oil cooler is designed to reduce heat
of the engine by way of the engine oil which is ran through the cooler. This cooler
utilizes radiator coolant which is ran through cooling fins to transfer heat. When
this cooler fails it can cause engine oil to be released into the cooling system
or leak externally.
Removing Serpentine Belt
The engine's combustion chamber can reach temperatures of up over four thousand
degrees Fahrenheit. About thirty percent of the fuel is converted into actual power,
and the remaining seventy percent is developed 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
which is controlled by the thermostat.
Car manufacturers have found that a 195° thermostat is optimum for efficiency.
Below this threshold the catalytic converter will not work properly which will produce
In the beginning, water was used for cooling systems, as it's the most efficient
fluid to absorb and dissipate heat. The disadvantage of using water is that it freezes
at a higher temperature and, boils at a lower temperature than coolant besides causing
Eventually, water was mixed with ethylene glycol, which worked as an anti-freeze
agent, it also increased the boiling point of the mixture. Low levels of coolant
can lead to problems related to engine overheating.
Engine Oil Cooler Cutaway
Article first published 2016-02-03