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By Allen L Phillips

When Henry Ford built the first Model T Ford in 1908 he installed an internal combustion engine.  Most cars and trucks today still use similar internal combustion engines, although considerably advanced from the one Henry used.


Today’s engine is said to be 25% efficient.  That means that only 25% of a gallon of gas is converted to the energy that operates your car.  The other 75% is converted to heat and that heat must be managed.  Your engine cooling system manages that heat.

How it works:  A key component of any cooling system is the radiator which is an assembly of many small metal tubes to which are attached thin metal fins.  Filled with coolant and located at the front of the car, the radiator is exposed to the wind as the car moves.  The engine is placed right behind the radiator and between them is a cooling fan, driven by the engine, which helps pull air through the radiator. 

Because of the heat produced, automobile engines are (and always were) designed with internal hollow spaces around the combustion chambers. Coolant flows through these spaces to control the heat produced by the combustion process.  The heated coolant travels out the top of the engine, through a rubber hose, into the top of the radiator.

As the coolant moves down through the radiator, heat is absorbed into the metal tubes and fins and radiates (thus the name “radiator”) out into the  passing air.  The cooler water then moves back into the lower part of the engine through another rubber hose.


Some History:  The simple cooling system in Henry’s first Model T consisted of the cooling radiator, the cooling fan, the engine and water.  Henry initially took advantage of the thermo-siphon effect, the natural tendency of hotter water to rise, to circulate the cooler water from the bottom of the radiator into the bottom of the engine and the heated water out the top back into the radiator. 

Water pumps were soon added to better circulate the cooling water and in the mid 1920’s thermostats began to appear.  The thermostat, still used today, restricted the flow of water until it warmed up so that the engine reached an efficient operating temperature more quickly.  The thermostat also allowed better operation in cold weather, when engines might not otherwise warm up, and facilitated the addition of a heater for the car’s occupants by using hot water from the engine cooling system.

More and more cars on the roads eventually led to traffic which exposed the weakness in the cooling systems.  When the car slowed or stopped and the cooling fan and water pump both turned more slowly, the system was unable to carry away heat fast enough.  The result was a “boil over”, the common term back then to describe what happened when the cooling system couldn’t cope and boiling water came out of the vent.  (The cooling systems had to be vented because the pressure caused by any overheating could split the radiator open.)

In the 1950’s pressurized cooling systems were developed using a pressure cap on the radiator which sealed the system but would release water when a certain pressure was reached.  The early systems would release at 6 or 8 pounds per square inch (PSI) while today’s cooling systems are designed to operate at pressures of 12 to 16 PSI.  This allowed engines to operate at higher temperatures with improved efficiency.

“Coolant recovery” systems also became common during this period.  This consisted of a plastic tank that would hold several quarts of water, into which the hot water escaping past the cap would go.  Then as the radiator cooled down the water would be drawn back into it from the tank.

Also in the 1950’s & 1960’s, the terminology began to change as the use of water in cooling systems gave way to “coolant”, a mixture of chemicals and water primarily to inhibit corrosion.  That was the iridescent green coolant that was so common until recently. 

Today:  Your car’s cooling system doesn’t just cool but actually manages engine temperature to keep it within the heat range specified by the manufacturer.  And Henry’s use of plain water in the Model T has evolved to the use of very specialized coolants in various formulations and colors, all specific to the make and model of car.

Maintain your cooling system:  Manufacturers formulate their coolants to protect, and be compatible with, the various metals and plastics (yes plastics) used in their engines.  Using the wrong coolant can damage your engine and void the warranty.  Never allow different coolants to be mixed together and make sure that only the coolant specified for the make and model of your car is used.

Coolant also loses its protective ability over time and needs to be periodically replaced.  Follow your manufacturer’s maintenance schedule for this service.  All reputable shops will have various coolants on hand, one of which will meet your manufacturer’s specifications.

Monitor your cooling system:  In the early days of the automobile overheating was common and engines were built to withstand most of these events.  More recently, federal gas mileage mandates and cost cutting pressures have caused manufacturers to trim excess weight to the point that few of today’s engines will withstand a serious overheating.

Watch for warning lights and/or messages regarding engine performance.  If you see any indication of overheating stop the car as soon as possible and call for help.  Continuing to drive could result in an overwhelming repair bill.  Many current engines are not repairable after being severely overheated and replacement can cost from 5 to 10 thousand dollars.

Do it yourselfers beware:  The fact that your engine cooling system is under pressure makes it dangerous to open the cooling system when the engine is still hot.  When pressure in the system is released the coolant can suddenly boil and cause severe burns.  Wait for it to cool down and/or leave it to the experts.

Inspired by an article on the Alldata website;  When Cooler Heads Prevail by David Bry.


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