On my 'new. car (late '94 405SRDT) I thought the PCV valve (that clips onto the end of the Intercooler) was u/s. We...ll after my exploration it is now! Has anyone got a spare as it will be 3-4 weeks for replacement. (I would even be interested in a loaner)
I now know how the valve works: It is normally open (hence my thinking it was u/s) It operates when the inlet pressure (ie crankcase) is lower than air pressure. There is a diaphragm open to air one side (via a weep hole) and the other side is to the crankcase.
I personnally can't think of a time when the valve would be closed, as the piston movement must cancel out any crankcase vacuum, and the blowby would tend to pressurise the crankcase anyway - so stopping the valve from working. Any ideas??