PCV Valve
#1
12-05-2017, 08:33 AM
PCV Valve
Dear Forum,
There are a number of posts and threads in this forum regarding PCV valves. For example:
https://www.jaguarforums.com/forum/x...2/#post1430504
Nobody appears to have reached any real conclusions regarding how a PCV valve should behave? For my part, I have found the following:
My PCV Valve doesn't rattle and doesn't block flow in either direction. However, if I block the pipe that fits into the Cam Cover with my thumb and suck on the pipe that goes to the inlet, I can hear/feel the diaphragm closing against the spring and as it does so air is drawn in through a tiny square hole let into the underside of the outer rim of the valve body (presumably to allow air in on the non-functioning side of the diaphragm, so that it can be drawn against the spring). If I remove my mouth, the spring returns the diaphragm and expels air through the tiny hole as it does so.
However, if I block the pipe to the inlet and suck on the pipe to the Cam Cover, the valve closes and remains closed when I remove my thumb but continue to maintain the sucking 'vacuum'?
If I block neither pipe I can blow and suck through both pipes with no effect whatsoever?
Now what is puzzling me is that if this valve is designed to allow crankcase pressure to escape, yet is controlled by the strength of the vacuum from the inlet manifold, then surely the inlet manifold 'sucking' and the crankcase 'blowing' would mean that the valve would always be open? How is this a 'controlled vacuum leak'?
Are the pipes on opposite sides of the diaphragm and the correct balance is achieved by virtues of the strength of the return spring versus either the expelled crankcase pressure or the strength of the vacuum?
Bottom line is, does anyone know whether (given my clumsy testing) my valve is functioning okay - Otherwise it will cost me £30 for the valve and £25 for shipping it to Dubai, so PLEASE - What do you think?
Regards,
Ray
There are a number of posts and threads in this forum regarding PCV valves. For example:
https://www.jaguarforums.com/forum/x...2/#post1430504
Nobody appears to have reached any real conclusions regarding how a PCV valve should behave? For my part, I have found the following:
My PCV Valve doesn't rattle and doesn't block flow in either direction. However, if I block the pipe that fits into the Cam Cover with my thumb and suck on the pipe that goes to the inlet, I can hear/feel the diaphragm closing against the spring and as it does so air is drawn in through a tiny square hole let into the underside of the outer rim of the valve body (presumably to allow air in on the non-functioning side of the diaphragm, so that it can be drawn against the spring). If I remove my mouth, the spring returns the diaphragm and expels air through the tiny hole as it does so.
However, if I block the pipe to the inlet and suck on the pipe to the Cam Cover, the valve closes and remains closed when I remove my thumb but continue to maintain the sucking 'vacuum'?
If I block neither pipe I can blow and suck through both pipes with no effect whatsoever?
Now what is puzzling me is that if this valve is designed to allow crankcase pressure to escape, yet is controlled by the strength of the vacuum from the inlet manifold, then surely the inlet manifold 'sucking' and the crankcase 'blowing' would mean that the valve would always be open? How is this a 'controlled vacuum leak'?
Are the pipes on opposite sides of the diaphragm and the correct balance is achieved by virtues of the strength of the return spring versus either the expelled crankcase pressure or the strength of the vacuum?
Bottom line is, does anyone know whether (given my clumsy testing) my valve is functioning okay - Otherwise it will cost me £30 for the valve and £25 for shipping it to Dubai, so PLEASE - What do you think?
Regards,
Ray
Last edited by EsRay; 12-05-2017 at 08:56 AM.