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Idiomas disponibles
HOW THE COOLING SYSTEM OPERATES
THE NON-PRESSURE SYSTEM
Cooling systems having to work under pressure are fairly a new thing. Up until the late 1950's, cars had low
compression engines and low horsepower; therefore, they did not develop the amount of heat modern
engines do. Also, cars had larger radiators and there was more room under the hood, enabling the heat to
dissipate. If the cars were kept in good mechanical condition, no cooling system problems would arise.
The boiling point of the coolant depends on the amount of atmospheric pressure exerted on it. As the
pressure exerted is decreased, so will the boiling point. Because the water pump, which is connected to the
intake side of the cooling system, develops suction, the pressure in the system is reduced. Although the
system may be working at a safe temperature, because of the fall in pressure, boiling can occur in the pump
inlet. This causes expansion of the coolant (vapor-lock) and not only slows the circulation down, but also
forces coolant out of the overflow. The remaining amount of coolant will overheat more easily.
Since the late 1950's, with the change to higher horsepower engines, smaller radiators, higher thermostat
opening temperatures - much more heat is developed with less room for the heat to dissipate properly. It
became necessary to improve the cooling system.
THE PRESSURIZED COOLING SYSTEM OR THE OPEN SYSTEM
This system was developed to eliminate the above problems. In a pressurized cooling system, the increased
pressure is isolated from atmospheric pressure. The boiling point is raised by approximately 30F for every
pound of pressure exerted on the cooling system. Coolant will reach 2500F before it will boil in a cooling
system under 15 pounds of pressure. At this temperature, because the coolant is still in liquid form, it will
circulate through the engine and cool the parts at high temperatures without boiling. The cooling system's
efficiency, therefore, depends upon all conditions and altitudes.
The radiator filler neck and pressure cap are the components pressurizing the system.
The filler neck consists of an upper and lower sealing seat and an overflow tube. The lower sealing seat is
engaged by the pressure limiting valve of the cap, while the upper sealing seat (in the open system) is
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