Idiomas disponibles
Idiomas disponibles
3. A stainless-steel pressure valve spring which seals the pressure valve against the lower sealing seat of
the filler neck, permitting pressure to build up as the coolant gets hotter.
4. In the pressure valve itself, there is a vacuum relief valve which is either weighted in an open position or
closed with a spring.
THE CLOSED TYPE OR CONSTANT PRESSURE TYPE OF VACUUM RELIEF VALVE
The vacuum relief valve is kept closed by a spring while the engine works to build up pressure. When the
engine is turned off and begins to cool off, a partial vacuum forms which opens the valve to release excess
vacuum in the system
THE OPEN TYPE OR WEIGHTED TYPE OF VACUUM RELIEF VALVE
The pressure vent type of cap makes use of this type of vacuum relief valve. It is built in a way that the
vacuum valve hangs loose and is weighted down with a calibrated weight.
During rapid heating and overheating situations, the pressure built-up pushes the vacuum valve up, causing
the cap to operate like a constant pressure cap. When the engine is turned off and the system cools, the
vacuum valve falls back to an open position.
Systems utilizing radiator caps with this type of vacuum relief valve exert less strain on the hoses, radiator,
and water pump seal. When located near the intake side of the water pump, this mechanism allows coolant
to reenter the radiator from the reservoir due to water pump suction during acceleration.
ROUTINE CHECKS IN THE OPEN SYSTEM
To remove the pressure cap for routine checks of the coolant level, make sure the engine, radiator and cap
are not hot.
Make sure engine is turned off, allow the radiator to cool (this can also be done by lightly spraying water on
the radiator core). After the cap has cooled, use a cloth to turn the cap counterclockwise to the filler neck
safety stop, leaving it in this position until all pressure is released (in this position, the pressure valve
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