View Full Version : What is the purpose of the pcv valley
The valley where the pcv sits has oil in it sometimes. I assume the two circular things are valves that allow oil to move in or out. What is the purpose of this area?
LowKeyLoki
03-31-2023, 08:46 AM
The valley has separate Channels that allow coolant and crankcase vapors to pass through the Pcv system. If oil is pooling in the valley around it you need to replace you Pcv asap, as eventually cooalant and oil will be able to mix and can hydro lock or destroy vital components.
Get it looked at ASAP!!!!!
I’ve removed the pcv, and looking at the open space where the pcv was. There was a small pool of oil there. I have a new pcv but was just curious what that area does. Thanks for the reply.
LowKeyLoki
03-31-2023, 12:53 PM
Sorry I thought you meant the area above the Pcv where it seals to the block. Oil pooled in the valley below the Pcv is normal when you remove it.
Smac770
03-31-2023, 02:46 PM
The "PCV" as everyone calls it serves several functions. One is to pass fresh air from the intake path to the crankcase. This is the small hose from the intake path. Another is to receive crankcase gases via the cylinder heads to fine filter the oil out of the gasses. The oil is passed back down through the triangular drains into the reservoir and the gasses are passed up to the supercharger.
https://www.shopdap.com/06e-103-547-ac-vw-audi.html , specifically
https://www.shopdap.com/pub/media/catalog/product/cache/ecd051e9670bd57df35c8f0b122d8aea/0/6/06e-103-547-ac-------.jpg
The neck has an in and out port, but only the in port is used on the 3.0T. The cleaned gasses out path is the small tube on top to the supercharger. The cleaned gasses out path in a naturally aspirated version like the 2.8L or 3.2L would be the out port in the neck. But you see the out port has just a plug in it on a 3.0T.
https://www.audiworld.com/forums/attachments/q5-sq5-mki-8r-discussion-129/79370d1501280110-q5-fsi-carbon-build-up-dd.jpg
I always wondered why all the talk about coolant with the 3.0T PCV. But I guess it makes sense given it's location. Still seems risky. Develop a leak in the o-ring of any of those three openings and you've got coolant going right into the crankcase.
As for in the drip reservoir, I assume the pathway for the oil and fresh air to the crankcase is that opening in the back as seen at this moment: https://youtu.be/wHUihyRk4mA?t=1173
I believe the check valves are not involved in the PCV return path; they just happen to be accessed there. If you look at the oil block diagram for the EA837 on pages 28-29 of SSP 411, I believe the two check valves there are item 18, pathway from the oil filter to the cylinder heads, one check valve for each cylinder head. We see in the video at that moment how there seems to be a channel from each check valve to a different side of the engine (cylinder head).
Thank you both! This makes total sense now. One thing I was missing was how the oil was returned from the pcv, I didn’t realize that was what those triangular things do.