How to keep your cool

The engine in your car is air cooled—it uses an antifreeze/water mixture as a medium to transfer heat from the engine to the coolant and then coolant to the atmosphere through the radiator.  Because this fluid is asked to do so many things and its function is to transfer heat, it has some peculiar characteristics.  First of all, straight water (H2O) transfers heat well—but it boils at 212 degrees and freezes at 32 degrees—hardly acceptable by itself for this task. Automotive Engineers discovered that mixing 50% ethylene glycol with water would raise the boiling point of the water to 235 degrees and drop the freeze point to -34 degrees and it would raise the viscosity of the coolant (the resistance to flow) allowing the water pump to circulate 50% more coolant-- improving heat transfer and dropping engine temperature!

Because the engine coolant is in a sealed system with a variety of metals—ferrous (cast iron and steel) and non-ferrous (aluminum, brass, and copper)—these metals will rust and corrode because they are exposed to oxidation and will deteriorate rapidly without chemicals to protect them.  The additives in antifreeze will protect these parts by boosting the pH--the alkalinity or acidity of a liquid—as well as anti-foam agents, lubricants, and rust and corrosion inhibitors.  But like any chemical in a high temperature environment coolant loses its ability to protect these parts after 1 year of use and the coolant must either be replaced or additional additives added back to the fluid to insure protection.

When a cooling system is not serviced regularly rust, scale, and corrosion will accumulate inside the engine block, cylinder heads, radiator, and heater core—restricting coolant flow and slowly eating away metals to cause parts failure.  Your water pump, radiator, freeze plugs, head gaskets, intake gaskets, and heater core are usually the first parts to fail and although they are relatively inexpensive the labor charges to replace them are not.  It is not unusual for a shop to bill 6-8 hours of labor to replace a heater core (a $80 part, for example) on some vehicles because the whole dashboard has to be removed to do the repair!!!  So you can see that regular cooling system service can be money well spent!

For more information on cooling systems see: HowStuffWorks "Cooling Systems"