MotoRad MT-300 Manual De Instrucciones página 6

During rapid heating and overheating situations the pressure built-up pushes the vacuum valve up, causing the cap to
operate as 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 water 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, and 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 counter-clockwise to the filler neck safety stop,
leaving it in this position until all pressure is released (in this position, the pressure valve pressure is lifted from the
lower sealing seat of the filler neck allowing for the pressure to subside). With the cloth, proceed to remove the cap by
pressing the cap down to allow the cars to pass over the safety stops. Check for traces of liquid or steam around the
rim of the cap and overflow tube when removing the cap. Also, make sure the overflow bottle vents and overflow tube
are open.
ROUTINE CHECKS IN THE CLOSED SYSTEM
There is no need to remove the pressure cap. Coolant level can be checked in the reservoir and be added to the
reservoir. Although routine removal of the cap is not recommended, it should be replaced just as often as open cooling
systems caps or when coolant is replaced. Since the filler neck safety stops on the closed system are steeper and
higher, to remove the cap, it will be necessary to press down very hard. Do not force off with a tool because this may
damage the filler neck and/or solder joint.
During routine checks also check the gasket. Make sure it has not deteriorated or become brittle or cracked.
Note: Pressure caps should always be tested for proper pressure release levels. Specifications require that the cap
must open below the high limit of the pressure range and must not leak below the low limit of the pressure range.
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