pcv delete

[alldaboost]

I just bought an a4 1.8t 04 and the seller told me the downpipe was leaking, when i got home i discovered problems with the pcv system. i was surprised to see how complicated it was. Why is there 2 cranckcase vent ( one on the valve cover and one on near the oil filter housing)? Its the first time i see something like this. Did anyone ever try blocking one off? Im tempted to block the oil filter vent and only use the one on the valvecover. I would run a pipe from the valve cover to the turbo intake and call it a day. what do you guys think?

[alldaboost]

Anyone?

[Mike Tries]

I wouldn't mess with it. How are the valve train and crank case connected to each other? Oil return passages? VW felt the need to ventilate the crank case separately, probably because they couldn't do it as well from just one port.

[willemml]

You probably want to keep both vents, otherwise the pressure differential between the crankcase and the valve train could cause issues. Correct me if I am wrong, but I'm pretty sure the block and the head are mostly separate and connected only by the coolant and oil passages. That pressure differential will try to equalize somewhere, and the path to equalization may not be where you want if you remove the one that VW designed.
I don't actually know though, just guessing...

Edit: I see Mike Tries beat me to it, didn't reload before posting haha

[grayjay]

It is a turbo motor, not a simple NA motor. When intake manifold pressurizes under boost, the PCV closes and no vacuum is being pulled on crankcase but you still have piston blowby occurring that needs to be dealt with. The hose from top of the valvecover is not a 2nd PVC but is connected to a pressure relief valve (PRV) that allows fresh filtered air to flow into crankcase while there is vacuum in intake, then it switched direction and allow for continued blowby evacuation from crankcase while under boost. The diaphragm in the PRV chokes down the available (reversed direction) air flow during turbo pressure operation so that too much unmetered air does not get pulled into intake from crankcase. The PRV diaphragm does fail and PRV should be replaced every few years, it is definitively a wear item. The crankcase ventilation system is fairly complex, much better idea to maintain it rather than just ripping out. There is a lengthy thread about doing that with a catch can, but I would highly advise just maintaining rather than defeating the system.

[JDCinATL]

Search "Old guy"s posts about the evap/emission system on our cars. It is a mess, compounded by model year differences as well, but his posts and associated discussions help clear it all up.