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EA82 Oil in Air Box/Intake Mystery


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Hello all! I am posting because I'm trying to figure out exactly what is going on with my engine in my Loyale. For a while now, I have been having oil in my air box and intake snorkel. I have done a lot of work on this engine already, and with a baby on the way, I need it more reliable than ever. I'm due for a tune-up, but I don't want to spend money on an air filter and spark plugs when they're just going to get ruined again. Here's my issue:


I have oil coming into my air box, and a pretty decent amount at that too. The whole bottom half of my air filter is covered in oil, with it puddling up at the bottom. The whole rubber intake snorkel going to the throttle body is coated with oil on the inside, pooling up in the grooves of it. My throttle body and inside my intake manifold remain clean, however. When I engine brake down long hills is when it seems to be happening, since when I get to the bottom of the hill and touch the gas, I get a cloud of blue smoke out the exhaust (temporarily), oil burning smell, the engine hesitates, and then goes back to normal when the oil is burned off. Going up hills and normal flat driving don't yield any abnormalities, and I can't see any blue smoke out the exhaust (from the rear view mirror).


First things first, I took care of the obvious. Replaced the PCV valve with a genuine Subaru one and replaced all the PCV hoses. The T connections are free and clear, and I even have the updated design with the blue T fitting, and it's installed properly (don't have the T fittings switched around). I also have taken care of just about every single vacuum line in the engine bay since most were hard and cracking. When I replaced everything, the problem still continued, though arguable it got a little better, just a little.


So the mystery is why is it still doing this? Just the other day I removed all the lines and PCV valve, made sure where the PCV valve goes into the intake manifold is free and clear. I have cleaned all the hoses and air box, but after just a drive or two, it goes back to the condition it's in now. Oil in the air box and intake snorkel, oil coated PCV lines lined on the inside with milky residue, similar to what you would find on an oil cap on an engine with head gasket issues. I presume this is just condensation, and it's worth noting that the oil cap has been replaced (it doesn't rattle; it seals properly) and it has no milky residue whatsoever. The oil in my air box becomes so much that it leaks out the bottom, spilling oil on my frame rail right underneath the air filter and eventually going onto the ground.


What is this telling me? With all the basics covered and what all my extensive research has yielded, one can simply pass this off as blow-by. This doesn't make me a happy camper because again, I have a baby on the way so I can't have things like leaking piston rings. I had the piston rings go out on my old Loyale and I don't want to deal with that after the baby is born, so I'm trying to take care of things ASAP and fix everything properly, so my car is the last of my worries and I can focus my attention on the baby. So let's get into further diagnostics! I have a vacuum gauge hooked up in my car, and it reads perfectly. Like, I have not seen a vacuum gauge give more ideal readings on an engine. At idle when warmed up, it sits beautifully at around 22-23", like it should. The vacuum gauge is very responsive to throttle inputs and never fluctuates or crazy needle vibrations (my old Loyale had erratic readings on the vacuum gauge, indicating piston ring issues, and sure enough they went out on me). So according to the vacuum gauge, my engine is in good shape, at least the bottom end is.


Today I did a compression test on the engine to see if it would yield any interesting results, and sure enough it did. The two cylinders on the passenger side of the engine (2 & 4) came out both at exactly 120 psi. However, the two cylinders on the driver's side (1 & 3) came out to exactly 60 psi. Obviously something is going on with that side of the engine. First idea for this would be my exhaust leak. The exhaust studs on that driver side cylinder head are completely messed up. When I bought the car, one exhaust stud was missing and the hole was oversized. Last time I had the engine out, the other stud decided to break off in the block. With careful attention to detail and help from coworkers at the shop I was working at, the best I could do was drill a hole in the broken stud, but we kept breaking drill bits because it was so hardened. Currently, the exhaust is barely being held on on that head, but it's sketchy to say the least. Bottom line, if I unbolt the exhaust, I don't know if I'll be able to get it to tighten again. I need a new cylinder head on that side to fix the problem, but I've been putting it off since I don't want to deal with all that work. So I have a minor exhaust leak from the bottom of that cylinder head (as well as a muffler about to fall off, getting a new one next paycheck though), and I'm not sure if that would affect compression test results but it is worth noting.


My question is, where do I go from here? Obviously my next step is a leak down test, but it might be a short while before I can get my hands on a leak down tester and air compressor (might be able to do it at the shop I work at, but finding time is hard). So I'm looking for some advice as to what it might be. I am more than happy to throw "new" (used, but machined) heads on the engine and do the head gaskets, but if it's the piston rings, I'd be looking at changing out the long block since I don't have the tools or extra money to rebuild the block. I would much, much, much rather do the head gaskets. It'd be nice to know that they've been done and I've got a lot of new parts on this engine (replaced just about every oil seal/gasket, brand new lifters, timing belts, etc.) so it would already make the job that much easier/cheaper. Oh yeah, last thing to mention is oil and coolant consumption. I do not lose any coolant, as the coolant level in both the radiator and the overflow reservoir stay steady and topped off. However, even after replacing all the oil leaks, I do lose oil. About 1 quart every 1800 miles or so. Usually by the time I do my oil change at 3000, I have had to add about a quart and a half. Sometimes a little more, sometimes a little less. 


If it's blow-by, that means my rings are shot, yeah? If that's the case, then why is my vacuum gauge reading perfectly fine? Even if it was my valves having issues, that would be obvious on the vacuum gauge. So assuming the gauge is telling me the right things, then that means that I'll be needing to do the head gaskets and throw on some rebuilt heads with good valves and seals. But if THAT is the case, why is oil getting into my PCV and intake? The only thing I can think of is the valve seals letting oil in or something, but again, I feel like I would notice that on the vacuum gauge. Now I've never done a head gasket job before so I could be ignorant about small details inside the head that can cause things like this, but it's not outside my realm of what I can do/learn. Would the exhaust leak on that cylinder head affect compression reading? Would I fix the compression by replacing the head and fixing the exhaust? If so, how/why would that affect the oil getting in my intake?


Any help is appreciated, even if it's just spit balling an idea. The baby is due in July and I'm trying to get this thing running like a top by the beginning of summer so I don't have to worry about my car. I could, and might, install an oil catch can just to ease the stress on the engine, but like I said, I like to get things done properly instead of just bypassing the issue. Thank you so much for reading all of this, I know it was a lot. I just try and give as many details as I can. I work as a technician and I know the smallest details can affect diagnostics a lot.  :)



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Some things to think about & consider:

Exhaust manifold being loose has nothing to do with compression test results. 

Compression that low should show up as poor running, I would think. 

Blown head gasket would almost certainly be blowing exhaust gasses into the cooling system.

Except, if the 2 cylinders have a leak between them, which would also explain them both having the same low reading.

Lots of blow by can push oil up everywhere.

How many miles on the engine?

Might be worth checking the timing belts / marks for proper orientation.

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The engine runs fine, runs pretty well actually! No real shortage of power, maybe a very slight misfire at idle but I blame that on old spark plugs, wires, air filter, basic maintenance stuff. Compression that low would be a reason for the misfire too, but regardless, you can't really tell it has two low compression cylinders based on how it runs. I just went outside and checked the timing, and it is spot on. One cam is 180 degrees off of the other. I even counted the teeth to make sure it didn't jump a tooth. I've done quite a few timing belt jobs on these engines, easy as pie, haha.


Yeah, I have had no indication of a bad head gasket. Has never overheated as long as I have owned it, coolant level has always been okay (and is still green like the day I put it in), no milky residue anywhere but the PCV lines, no coolant out the exhaust, and no exhaust gas smell in the coolant. Not that I'm ruling it out entirely, but I just haven't had any symptoms of a head gasket issue. Like you said, if they have a crack between them, it might not show up. The car has like 227k on it, but the engine isn't original. As far as I know, it has fewer miles than that. I don't have an exact number, but I would put it around 180k.


Would a head gasket leak between two adjacent cylinders cause blow-by? If so, then that would probably be my answer. Until I do a leak down test, of course. Oh yeah, I forgot to mention the spark plugs. When I pulled the plugs for the compression test, they all 4 looked pretty similar, even between the two sides of the engine. The driver side plugs were a little more oily than the passenger side ones, but all 4 just looked like old plugs. I looked up an image of spark plug diagnosis, and they look most similar to the "Ash Deposit" plug in the following image (http://www.aa1car.com/library/reading_spark_plugs.jpg). According to that, it's due to oil burning from faulty valve guide seals.


Thank you so much for the response!

Edited by jj421
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I had that problem of oil in my air filter and air intake.  Turned out to be the oil pump was leaking and the oil coming out from around the pump was being sucked up into the air filter while I was driving.


Repaired the leak and haven't had any problem since. 


Look around for leaks, 

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Not directly - cylinder to cylinder...  I guess depending on what the valve positions are in the adjacent one, compression would get pushed out intake or exhaust.  Not sure how that would pick up oil.


Leakdown should be interesting.

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Huh, that's good information to know. When I had the engine out and I was doing the timing belts, I replaced all three of the oil pump seals. I didn't replace the actual oil pump, however. If I recall correctly, it is still oily down there so that might be the issue if the actual pump is shot. But that wouldn't explain the low compression unless I have two separate issues, a head issue and an oil pump issue. Hmmm


Really I just have to do a leak down test and that'll tell me exactly what I need to know. I just wish I had an air compressor so I test it easily. The shop I work at is usually pretty busy and the next day off I have that I can come in is next Wednesday, assuming they let me do it, haha.

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Have you tried removing the oil cap, starting it and put your hand (or hold a piece of paper over the top) over the oil filler to see if you feel air puffing out?


If all you need is an air compressor, come over to my place. I also got a flexible camera to look in the cylinders.

Edited by MR_Loyale
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Leak down test has been done! My boss had today off and my coworker let me borrow his leak down tester, so on lunch I pulled my car into the shop and did the test. First, let me respond to you guys:


DaveT, I did manage to do the shaft seal last time I had the engine out. I made sure to get an oil pump gasket set that included all three parts to the oil pump. Either the mickey mouse gasket got misplaced on installation, the oil pump itself is bad, or something else is causing it to get oily down there. I replaced the crank seal too when I was there.

MR_Loyale, hmm, no I haven't tried that yet. I can do that at lunch tomorrow. Thanks for the offer on using the compressor and camera! 

Dee2, well now that I have the leak down tests, tell me if you think they're related or not.


Second, here's the results for the leak down test. I only did the test on cylinder 1 and 3 (driver side cylinders) since those are the problem cylinders and because I only had so much time on my lunch break. I feel pretty good about the accuracy of the tests; I made sure they were at top dead center (used a small piece of tissue paper to ensure it was on the compression stroke, and peered in with my flashlight to make sure the cylinder was indeed at the extent of its travel). I also was using an expensive MatCo leak down tester, not some cheap Harbor Freight one. So here are the results:


Cylinder #1 (Driver side, front of engine)




As you can see, it was sitting at around 24% leakage, which is a little on the high side but nowhere near what I expected for having such low compression. Where was the air escaping? Well, judging off sound, about 2/3 of the air was coming out of the crankcase (could hear it coming out of the oil filler tube, dipstick tube, and PCV hoses). A little bit of air, about 1/3, was coming out of the throttle body/intake, definitely audible when I opened the throttle (had the intake snorkel off). No air coming out of the exhaust, no air coming out the radiator/cooling system. Just the crankcase and intake.


Cylinder #3 (Driver side, rear of engine towards firewall)




As you can tell in this picture, this cylinder was right in the 12-13% leakage range, which is not bad at all. In fact, that's actually pretty good! Similar to cylinder #1, about 2/3 of the air was coming out of the crankcase and about 1/3 was coming out the intake (again, rough estimates just based on how much air I could hear). Still no air escaping out the exhaust or cooling system. 


It's also worth mentioning that I could not hear air escaping between the cylinders either, both cylinders were independent. So what's my interpretation of these results? Well, since the majority of the air was coming out of the crankcase, this is telling me that my piston rings are not sealing very well. I also have air coming out the intake, so that tells me the intake valves also are not sealing properly, thus requiring rebuilding the cylinder head. However, because of the relatively low percentage of leakage in both cylinders, this tells me that neither my piston rings nor intake valves are in that bad of shape. In other words, in theory (correct me if I'm wrong), if I replaced the head gaskets and put on rebuilt heads with strong sealing valves, this will lower my leakage percentage. Even without touching the piston rings or bottom end, cylinder #1 should get reduced to a more acceptable level (hopefully below 20%) and cylinder #3 should be reduced to probably around 10%.


However, even at 24%, this doesn't directly explain the low compression (again, correct me if I'm wrong). It definitely doesn't explain cylinder #3, because at 13% leakage I should not be down to 60 psi of compression. So what does low compression, minimal leakage mean? From what I was reading online (not a whole lot of information on this condition), it usually means a valve train issue or the timing is off. If it's a valve train issue, like I said in the above paragraph, a cylinder head rebuild would be the route to go. This would also raise compression if this is the issue.


If the timing was off, that would definitely explain the low compression. But even at one tooth off, it's pretty obvious how poorly the engine runs when the timing is messed up, especially to someone who is familiar with these engines. Maybe it's worth re-doing the timing belts to make sure everything is properly timed, but that doesn't explain the oil in my intake (unless I have separate issues). However, the fact that I'm getting air past my piston rings, coming through my crankcase and PCV system, gives me a pretty good indication that that is why oil is getting into my intake (especially if the intake valves aren't closing properly). 


What's my next step? Well, to me, it seems like putting on rebuilt heads and doing the head gaskets is the fix. Though I am exhibiting piston ring wear, I don't think it's that bad since my vacuum gauge doesn't pick up on it and because 95 psi of compressed air coming out of the crankcase probably makes it sound worse then it actually is. What worries me though is the fact that the majority of the air is coming out of the crankcase, and not the intake. I don't want to do head gaskets on an engine with really bad piston rings. That being said, I also don't want to do the head gaskets and increase compression, ultimately putting more wear on the piston rings because that's the only place where air/oil can go. It would suck to tear apart the engine and do all that work, just to have the rings go out 6 months later.


So let me know what you guys think about these results, as well as my process of thinking. Correct me if I'm wrong on anything, I don't know everything and half of this is theorizing/information I found on the Internet. Thank you so much!  :)

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The reason you have low compression on both cylinders but only one shows higher leakdown, is that you have valves that are hanging up when closing. Based on your description, I'd say intake valves. I've had to do leakdown tests 3 or 4 times on a cylinder to catch a valve that was hanging up. The fact that you heard excessive air coming out the crankcase indicates worn rings which equals blow by. Is it bad enough it's soaking the air filter? If it's not, and it's not fouling out the plugs, then I wouldn't be too worried since the only fix is tearing it down, taking a snap gauge to check the cylinder bore and throwing in new rings. Providing the bore isn't scored. I'm not a fan of miracle in a can, but you could try Engine Restore. I have used it in the past with decent results but it only works with cylinder related issues. Got one cylinder bumped 40 psi.

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You should try  a leak down test on the good side, too.  If you get similar results, you will be certain that the rings are not the source of low compression on 1 & 3,  and it will also increase the proof that the blowby is due to worn rings.


Is the valve train on 1 & 3 particularly sludgy? Is there a valve lifter or follower that is out of whack?If intake valves are hanging open, there has to be a reason.  Maybe a good dose of engine cleaner (MMO or similar) would loosen up the situation? 

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90% of the time, valves hang up because the guide is worn or scored. The stem will catch in the guide when it tries to go back up at a slight angle instead of straight up as it normally would. It's not that it's actually hanging open, it's just hanging up for a fraction of a second or so as it's closing  and then coming to rest unevenly on the valve seat so there's only a partial seal.

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A lot of good information, thanks everyone!


Skishop69, yeah, I think for sure my intake valves are hanging up. I agree, the air going past my rings is what's causing my blow-by. I think that in combination with my intake valves acting up is what's getting oil into my intake. My air filter does indeed get soaked in oil. Well, at least the bottom half. Not sure how bad it is fouling the plugs, I haven't replaced the plugs since I bought the car almost a year ago (about 15,000 miles ago), but they weren't as bad as I expected them to be. Not that they were in great shape, but considering how much oil I believe my engine ingests, I expected them to be worse. That's good info on the valves getting caught up! That would explain the low compression if they aren't seating properly, mixed with the blow-by just to make things worse.


Robm, I don't think I'll be able to do a leak down test on the other side, probably not until next week, which sucks. Both valve trains are actually very clean; I always keep up with my oil changes and last time I had the cam towers off, everything look clean and sludge-free.


Dee2, that's good to know! I will probably try and do that tomorrow since I have the day off, but I've got things to take care of first, then if I have time, I'll post with the results.


So far it's seeming like my valves and valve guides are the main reason for my low compression. Rings are letting oil get past through blow-by and getting into the intake through improperly seating valves. I am going to do the wet compression test and get some results through that, hopefully confirming this.


I also think I might put some additives in the engine too, like you guys suggested. I'm not a fan of miracle in a can stuff either, but I might put something like Engine Restore (or another highly rated/reviewed product with confirmed good results) into the oil to help the piston rings, as well as running some engine cleaner through the vacuum lines to maybe try and clean up the valves. If the valve guides are problem, obviously that won't help much, but it's worth a shot for now. When I peered my flashlight into the cylinder, the top of the piston looked pretty carboned up, presumably from burining oil. I can't imagine the valves aren't in similar shape.


I find it interesting because the other day, I kinda swapped the PCV hoses around and I seemingly have less oil through the PCV lines. Before, the black T fitting was pointed towards the rear of the engine, and I moved it so it's pointing down towards the ground (if that makes sense) and routed the hoses accordingly. I just took a quick drive on my lunch break to get food and the PCV hoses aren't as oily as they have been. I rotated my air filter so the "dry" part is on the bottom, so I can see if it gets as oily as it did before. Tomorrow I will be driving a fair amount, so we will see.


So basically my next steps are as follows:

-Perform wet/dry compression test

-Add oil additive to help piston rings, drive for a few days

-Another wet/dry compression test

-Add cleaner through vacuum lines and drive for a few days

-Another wet/dry compression test


Obviously we will see what the results are on the first wet/dry compression test and go from there, but in my head, that's my plan of action. So far, I think I'm just gonna rebuild some heads and do the head gaskets, especially if an oil additive will help my piston rings. Also considering getting a parts car and building the engine, but with my tools at work and living in an apartment and no easy/cheap way to tow a car home, it might not be the most practical.

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Wet/dry compression test has been done! Some interesting results, so let's get to it. This was done on a fully warmed engine (spark plugs were hot to touch), and with wide open throttle. For each cylinder I did a dry compression test, cranking 8 times. Then I did a wet compression test, pouring in 2.5-3 cap-fulls of 10w-30 into the cylinder, cranking another 8 times. I also put in the past results too, for reference.


Cylinder #4: Dry(110psi)Wet(145psi) [Orig. 120psi] Cylinder #3: Dry(120psi)Wet(170psi) [Orig. 60psi, 12.5% leakage]


Cylinder #2: Dry(105psi)Wet(175psi) [Orig. 120psi] Cylinder #1: Dry(110psi)Wet(160psi) [Orig. 60psi, 24% leakage]


So a couple of things to mention. Number one, most obvious and confusing to me, are how cylinder #1 and #3 have decent compression now! Since the last test, they have double in compression, even though the only thing I have done to the engine is slightly move around the PCV lines. Only thing I can think of is maybe I didn't screw in the tester all the way into the spark plug hole, but I always check that it's tight before I crank the engine. Hey, at least they aren't as low compression as I originally thought, so that's not necessarily a bad thing.


Number two, it does indeed look like my piston rings are worn. With a pretty significant increase in compression once oil was added, it looks like I'm dealing with ring issues which definitely equals blow-by. However, the fact that I still have okay compression across all four cylinders, and that my vacuum gauge doesn't pick up on the ring wear, I think it's definitely worth a shot to put in a can of Engine Restore into the oil and see if it helps. Which brings me to my third point.


Third, the engine has seemingly fixed itself in regards to oil just getting dumped into my intake. I still see some oil in my PCV lines, but definitely nowhere near as bad as it was. I checked my air filter, and only a small section on the bottom had oil on it, in comparison to half of the air filter like before. This is after a full day of driving, including freeway use, hill climbs, hill descents (with engine braking), and full throttle acceleration bringing it near redline. I took brake clean and cleaned all the oil out of my intake snorkel and air box, and sprayed some in the PCV lines. I will check again in a few days to see the condition. 


The way I see it, I could do the head gaskets and rebuild the heads, but it wouldn't be worth all the time and money because of the ring wear. Might just look at getting another engine and in the mean time, run this one until it dies. Going to try Engine Restore and might even buy an oil catch can to prolong the life even more. But I think this engine is just tired and nearing the end of it's life. Let me know what you guys think, but I don't think it's worth my time and money honestly. 

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Looks like you're on the right track to me.  Compression looks ok.  Vacuum test is good cross check.  Oil problem is odd, just keep regular checks on it for a while to see if it comes back.  If other problems get worse deal with them based on new information.

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