Ето и какво пише в документацията:
OIL VAPOUR RECIRCULATION SYSTEM (BLOW-BY)
The emission of oil vapours is controlled by means of an oil separator which collects the vapours coming from the crankcase and from the tappet cover; the condensed vapours return to the sump via a pipe whilst the uncondensed ones are sent to the intake air hose via a pipe.
There is a regulation valve, on the inlet vapour delivery pipe, with a spring that in normal conditions acts on a diaphragm keeping it open, thereby allowing the flow of oil vapours coming from the oil separator.
When the vacuum inside the pipe overcomes the calibration of spring, the actual vacuum moves the diaphragm thereby closing the duct from the oil vapour separator preventing the intake of oil from the sump.
Накратко, както казва OEM, клапанът би трябвало да стои затворен над някаква степен на подналягането във всмукателния тракт.