('09-'13) Oil found in pcv lines? - Subaru Forester Owners Forum
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post #1 of 4 (permalink) Old 04-20-2019, 10:43 AM Thread Starter
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Oil found in pcv lines?

I need help figuring out why there is oil in one of the pcv lines on my 09 Forester X. It’s not the line that directly attaches to the top of the pcv valve, but the one that attaches next to / under the pcv valve. Thanks I’m advance.

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post #2 of 4 (permalink) Old 05-08-2019, 05:03 AM
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Hey there! I see you posted a couple months back, but I am having a similar issue, only with more problems, maybe? Since the day I drove my '16 Forester XT off the lot back in November, I have experienced dropping RMP's when applying the brake and/or the car will lurch forward 5 or 6 times at stop signs/lights. Only died one time last week. This has happened 90% of the time and I learned to just not apply the full on brake, but more eek my way to stops. Dealer has the car now and just can't seem to find the culprit...BUT...I had a seat cover replaced at another automotive center and asked them to just check it out while they had it and see if they could come up with anything. They found the PCV valve to not be functioning well, oil in the line (I think the same as the one you are describing) and a filthy dirty throttle body. And they found an old stored code P1603 of stalling AND they could replicate the problem. Well, then!...I was instructed to take it back to the Dealer (by the dealer service department) as it's still under Subie Warranty and to not let anyone touch a thing or else the warranty will void. I took the vehicle and the detailed diagnostic report to them on Friday to be worked on this Monday morning. Well dammit if they couldn't replicate the problem or find any old stored codes. I inquired if they checked the PCV valve and throttle body grime and of course I got the "well, yah, but that's normal for a turbo to kick out some grime, it's still not the problem". So, he was gonna take it to lunch that day and dink around with it. I took the initiative to pay $150 for a diagnostic check, they found the problem, and Subaru is fighting it all the way. Long story short, check your PCV valve and throttle body. Have you had any drive problems like I listed?

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post #3 of 4 (permalink) Old 05-08-2019, 05:51 AM
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Though Positive Crankcase Ventilation (PVC) systems vary by engine design they have been rather complex for decades.

As a general rule, when the engine's idle drops significantly, or the engine stalls, while applying the brakes, on a system that uses vacuum assist power brakes, there is a failure of a vacuum check valve or some other part of the intake manifold system, including the PCV system, that is allowing "Manifold Vacuum" to decrease to atmospheric pressure. In short, a very large vacuum leak is being created when the brakes are applied and the engine will loose rpm's to the point of stalling.

Excessive oil vapor build up in the PVC system and the throttle body could be a source of such a failure - or the symptom.

One of the reasons some manufactures strongly advise using care during oil changes not to exceed the maximum fill mark on the oil dipstick, and may even suggest not the fill to the maximum mark but remain between the minimum and maximum marks on the dipstick, is to minimize oil frothing or spray inside the crankcase which is then drawn into the PVC System and that may then overwhelm the oil /water vapor separator under certain operating conditions when there are high negative air pressures within the engine crankcase.

Servicing the PCV system regularly and removing oil and water vapor build up will minimize the problem as will regular air filter changes. Remember an engine is just a large air pump and needs to move air through all related systems efficiently.
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post #4 of 4 (permalink) Old 05-08-2019, 10:46 AM
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Well, the PCV is a maintenance item.
Oil vapor is what the crankcase would ventilate into the air if not for the Positive Crankcase Ventilation system, so the fact that oil is in a line on a 10 year old 2009...
Likely not indicative of a major problem.
Clean the valve if clogged.
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