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PCV Crankcase Breather Hole Sucking?

23K views 5 replies 2 participants last post by  VWRacing9079  
#1 ·
Heyo,

I just went through a horrible adventure of buying an '09 3.6, and a week after the purchase, the PCV diaphragm went, meaning lean codes and the Crankcase Breather hole on the valve cover was sucking air like crazy. I took it back to the dealership and they went to replace the valve cover and found valve damage supposedly though I didn't see symptoms. Thankfully, they just refunded us for the vehicle. I am stubborn so I am looking for another of the same vehicle.

TO MY QUESTION THOUGH: Should that crankcase breather hole on the valve cover ever suck air? Or is that always a sign that the PCV diaphragm is bad?

The reason I ask is that every Touareg I have test driven with the 3.6 is sucking air through that hole on the valve cover and I am obviously going to be sensitive to that now. I keep thinking maybe people just don't know that's a sign of a leaking PCV plunger or maybe it's supposed to suck a little? haha.
 
#2 ·
The PCV hole is used for sucking a small amount of air allowing the diaphragm to push the spring underneath when under vacuum.
The same hole is used to expel that small amount of air when the diaphragm goes up when there is no vacuum pulling on it.

Here is my 3.2 sucking and expelling air through the barb/nipple/hole. It's a different design than the 3.6 but I guess operation is the same. Vacuum pulls the diaphragm down. No vacuum the spring pushes the diaphragm up.
A torn diaphragm will allow air to be sucked continuously under vacuum (idle) and will also be letting air out when not under vacuum (throttle).
And of course engine is going to be rough and you will have low oil pressure warnings and blown valve cover gasket and what not.


I guess this is what you were experiencing:

 
#3 ·
A torn diaphragm will allow air to be sucked continuously under vacuum (idle) and will also be letting air out when not under vacuum (throttle).
Thanks for the reply! Most of the 3.6's I've looked at have constant suction at idle, so I thought maybe I was wrong. This last guy even took his to a shop and the shop told him it was fine/nothing wrong. I spoke to the shop and he didn't exactly sound 100% confident. There was no rough idle, but I was sensing a slight tickover. I'm thinking there is a small hole.