Now’s the time to have your engine coolant checked for freeze point before temps drop low enough to cause. The cooling system on today’s vehicles is complex as are the coolants (anti-freeze). The system condition is vital to the longevity and performance of your vehicle.
The cooling system is made up of coolant, a water pump, belt or chain, thermostat, radiator, radiator cap, hoses, freeze plugs, bypass system, heater core, passages inside the engine block, intake, and head(s).
The coolant is made of four components: water, ethylene glycol, dye, and a chemical package.  Water is used to cool the engine; ethylene glycol is used to lower the freeze point of the water; dye is used to identify leaks – it is not a reliable way to identify coolant type (Dexcool and Toyota red look alike, but are chemically different and should never be mixed).
The chemical package is the most important ingredient in coolant. It allows the cooling system to resist corrosion, scaling, and acid damage. It also contains nitrite (in most coolants), which mends protective-oxide film on metal when cavitation tries to wear it away. The chemical package does break down over time and stops protecting the cooling system.
The water pump circulates the coolant. The thermostat regulates the flow and temperature of the coolant. As the engine heats up the thermostat opens allowing the fluid from the radiator to circulate through the system. If the coolant is not hot enough it will flow back to the bypass system. The radiator has fins and tubes that coolant passes through allowing heat to be dispensed from the cooling system. The radiator cap is responsible for regulating pressure in the cooling system. The hoses transport the coolant between components. The heater core uses coolant to heat the interior or the vehicle and looks like a small radiator.
When an engine block is manufactured, a special sand is molded to the shape of the coolant passages in the engine block. This sand sculpture is positioned inside a mold and molten iron or aluminum is poured to form the engine block. When the casting is cooled, the sand is loosened and removed through holes in the engine block casting leaving the passages that the coolant flows through. Plugging these holes is the job of the freeze plugs. Freeze plugs can corrode and fail allowing the engine to lose most of its coolant – engine failure is most likely to occur when this happens.
All internal combustion engines have an engine block and one or two cylinder heads.  These surfaces are sealed together with a “head gasket”. When in good condition, the gasket keeps coolant from leaking out of the engine between the two component surfaces. Head gaskets usually fail if the engine overheats severely or continuously over time.
Before winter, and before summer you should have your coolant condition tested for freeze point and summer for boiling point. Failure to prevent freezing (or boiling in the summer) can result in costly repair.
Information provided by Paul Romesburg, owner  of Paul’s Automotive.