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06 2.5i (253)
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Discussion Starter #1
A friend with a 06 OBW 2.5 with a manual trans (only 113k miles) has quite a viscious oil leak that started just recently and I'm looking for help diagnosing it. When at RPM (e.g., 3k for 30 seconds or longer), oil will literally start streaming out of the back end of his motor. I cannot locate the source of the leak as it appears to come down above the crossmember and forward. It was falling from the passenger side but the front was on jackstands on uneven ground so I'm not sure how gravity would have caused the oil to flow.

To complicate matters, this vehicle has had a head gasket leak for years and despite the Exxon Valdez undercarriage, he assured me that he never ran low or overheated his motor. This does, however, make it a lot more challenging to trace oil leaks as you almost can't find a dry spot underneath. I can state pretty darn confidently that this primary leak does not appear to be coming from the head gaskets, VC gaskets, spark plugs, etc. It is possible, from my very limited knowledge, that oil could be coming from the rear of the oil pan, tough I'm leaning more toward the rear main or most likely the oil separator plate. From my reading, it seems that rear main seals tend to be pretty stout on the OBW. What is the probability of failure of these three seals (oil pan, rear main, oil separator plate)? My friend wants to know how much of a project he is looking at to determine if he should repair it or cut his losses and save his money for a new crosstrek.

Thanks for your help,
s
 

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Lawn ornament XT
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That era of the SOHC engine was known for oil leaks in the head gaskets. There is a pressurized galley that transits the gasket on the upper surface, and if that one leaks it can drip down and the drips can of course be blown back.

Maybe peek under the intake and see if you can spot the start of it up there?
 

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06 2.5i (253)
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Discussion Starter #4
First order of business is to clean / degrease everything which will make it easier to find the source! And we need to know 4 or 6 cylinder.
Agreed on degreasing. That was the job I left him with when I left. Hopefully that helps. As far as cylinder count, I thought 2.5 would have indicated it was limited to 4. My apologies.

s
 

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06 2.5i (253)
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Discussion Starter #5
That era of the SOHC engine was known for oil leaks in the head gaskets. There is a pressurized galley that transits the gasket on the upper surface, and if that one leaks it can drip down and the drips can of course be blown back.

Maybe peek under the intake and see if you can spot the start of it up there?
Our viewing was done on jack stands so much of the blowback would not be expected. Of course, degreasing the motor would also be of big help here too because while there is plenty of oil all over the motor (top included), I cannot be for certain if this is from his longstanding HG leak or if it is part of the newer streaming leak. Of course, your point is they could be one in the same. Are head gaskets known to leak this profusely if unfixed for a period of time (does this question sound as dumb to y'all as it sounds in my head)? I do very much appreciate also the anatomy lesson on the pressurized galley as this gives us a good lead to follow.

Thanks again,
s
 

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Any pressure leak can scale from tiny to huge, and head gasket failure is quite gradual.

The most common (pressurized) oil leak points are the emergency oil pressure warning switch, the oil control valves for the variable valve system and the head gaskets at the galley along the top edge where they carry oil from block to head.

The warning switch is at the centerline under the alternator. Its leaks tend to go down the front. The oil control valves are way out on the top sides of the heads. Leaks there go down the valve covers. Head gasket leaks tend to pool on top and then drain off the back near center.

All just guessing until somebody foams it clean and catches the fresh drip, but it might give you something to go on.
 

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When at RPM (e.g., 3k for 30 seconds or longer), oil will literally start streaming out of the back end of his motor.
To add to the possibilities mentioned regarding leaks at the top of the engine:

There's the engine oil pressure sensor (for the oil pressure warning light) - it's screwed into the top of the block, more-or-less under the alternator.

Another is the AVLS (variable valve lift system) oil pressure sensors. There's one at the top of each head -- at the back on the right side, and at the front on the left. (Photos of the sensors in this post ) In this regard, these sensors are subject to higher pressures, and therefore might tend to leak more, when the AVLS is in "high lift" mode. This typically occurs when driving with the rpm above 1600, or with the engine revved above 3000 in P or neutral.

As rasterman noted, there are oil supply galleries from the block to the heads at the top of the engine, one on each side -- toward the back on the right side, and toward the front on the left. This thread is a case in point; a head gasket leak at the oil gallery on the right side. The thread has a diagram of the oil system (post #5), and related photos.
 

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2001 Outback 5 speed, 2000 Outback Automatic, 2002 Legacy Wagon Automatic. All 2.5L
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Have you checked the transmission oil level? I had a front oil seal fail on a 5 speed that leaked horribly once the transmission got warmed up. I had to remove the transmission & crack the case open to replace the seal.
 
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