I’m trying to figure out a strange oil consumption issue after changing the pcv.
Car has 160000 miles and has always burned a moderate, yet consistent amount of oil, about 1qt per 2500 miles. No visible smoke or leaks.
I recently replaced the pcv with an OE Audi part, the old one was obviously shot. Diaphragm was cracked and stuck.
Now, the car belches a large cloud of smoke accelerating after engine braking. Obviously, high vacuum is sucking oil into combustion chamber or manifold. Oil consumption went through the roof whilst driving with normal compression braking. When I stopped compression braking while driving, oil consumption returned to previous amount (1qt per 2.5k).
My first thought was that I installed the pcv backwards. Most pcv systems im familiar with close when high vacuum is present on the manifold side, as to prevent sucking oil into the intake. Looking at some pictures online, it appears I installed the valve correctly.
I then removed the pcv to check it’s operation, and here is where I got a bit confused. It appears to function in the opposite flow direction as I would have thought. When I suck on the crankcase side, and cover the intake side port, it closes and seals. Yet, it never seals when vacuum is applied to the manifold side… the pcv is soaking in oil, so I’m sure that is where the oil is coming from, rather than valve guides/stem seals.
What is going on here? I find it hard to blame leaking seals as it only started when I changed the pcv. Compression test shows I do have leaking rings and low compression on 1 cylinder (120psi). The rest are all 150-160.