Publicidad
Idiomas disponibles
Idiomas disponibles
HOW THE COOLING SYSTEM OPERATES
THE NON-PRESSURE SYSTEM
Cooling systems having to work under pressure are a fairly 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 cooling system 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
smaller amount of coolant will overheat more easily.
Since the late 1950's, there are higher horsepower engines, smaller radiators, and higher thermostat opening
temperatures. Due to these changes, much more heat is developed with less room for the heat to dissipate properly.
As a result, 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. A 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 is able to circulate through the engine and
to 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 engaged by the spring
metal diaphragm in the cap. The pressure cap consists of two major valves which prevent radiator tanks and hoses
-1-
Publicidad
