The engine pictured is mine. The top red oval is where the PCV
line connects to the intake at back of engine bay. The middle oval is the snorkel end of the hollow tube and the bottom oval is the hollow tube connection to the valve cover.
The drawing marked Original
was created by someone else, I found it here: PCV system question... - V6Power Messageboard
It basically matches my engine configuration and likely billions of other cars. The drawing is same as zillions of other internet drawings explaining PCV
systems. It shows a flow loop as mention previously of intake>clean>crankcase>PCV>combustion.
In the drawing marked Ver 2.0
is where vacuum takes place. The whole intake - snorkel, throttle, upper & lower intake manifolds - all under the same vacuum The same amount of draw toward the cylinder heads.
So, in the drawing marked Ver 3.0
, if the same vacuum exists on both the PCV
and that tube plumbed ahead of the throttle, why do we think air will not be flowing toward the vacuum, toward the intake. I think both lines are being sucked on by the intake as shown in brown
. So I think contrary to popular legend, no real "clean air", no real loop of flow through the crankcase. Except for maybe a nano second when the throttle is being opened and perhaps there is a slight pressure difference between the PCV
line and the tube ahead of the throttle. But that difference in pressure is very short lived.
All this would explain why the entire snorkel and throttle get coated in oil. It isn't only because of a bad PCV
but a consistent flow of dirty air (oily air) up that front line ahead of the throttle. And seems that front line almost negates the reasoning for a PCV
valve since the snorkel tube does not have any kind of a valve.