JK 3.6 Liter - Oil in Air Filter

[OTH Overland]

Have a 2013 Jeep JK with 110k that we have owned for a little over a year. Until recently the air box never had a drop of oil inside, now suddenly we are getting quite a bit of oil coming in from the PCV fresh air intake line (running backward from valve cover to air box). Can not find a logical solution for this, searches online result in its a Jeep thing or the engine is going to explode..lol The oil started appearing on the air filter during our last trip to Death Valley, the only thing that stands out is while climbing over from panamint valley to Death Valley at fairly high rpm, we heard/felt a quick shudder/pop and the engine seemed to de-rate with a big loss of power. 3rd to 4th is a wide gap on the auto trans and tends to download a lot and run a higher rpm than I would like at the slightest hill. Since then we have made it back to Washington and done another 4k miles without any serious issues other than the oil mess.

Have since replaced the PCV valve (Thanks Jeep for making that a fun task) cleaned the hoses and air box, pulled all the plugs (look great no fouling or other issues), tested compression (a bit low at 100 cold, but all were equal), did a leak down test on all cylinders (at 100psi non had more than 2% loss, indicating valves,gaskets,rings are functioning properly) has decent vacuum at the crankcase to airbox vent which would indicate oil vapors should not be flowing the wrong way.

We are running a fuel economy tune on the engine, 35" tires with 4.88 gears, and a custom programmed transmission module (was installed after the issue occurred and made no difference to the oil, but greatly improved shifting). Jeep has been well maintained and never off roaded or abused (Until we got ahold of it anyway)

Jeep dealer has no ideas other than to let them 'tear into it' which likely will result in them taking forever and spending all my money until i end up with a new engine..lol

Looking to see if Mechanical types on here have any ideas, or have I missed anything as I am out of things to test at the moment. I will likely place a catch can inline ahead of the air box which should stop the filter getting soaked but does not fix the issue. Also if anyone knows of an independent mechanic in Western WA that works on the 3.6 that would be great. If we end up with major engine work it just might be time for a 392 or LS conversion.

Thanks

 

[zgfiredude]

Wow, you have done/thought of everything that I was going to suggest........I'll follow this to see what you learn!

Any lifter or rocker ticking? Does it run and idle ok otherwise?

 

[MazeVX]

Install a catchcan, it's a jeep thing and your engine is getting older and develops more blowby, maybe you run a different oil then before?
Different climate?
Steep inclines of camber and lots of throttle are typically causing this.

Eco tune will run leaner which is not always good but should not have caused this.

 

[OTH Overland]

Install a catchcan, it's a jeep thing and your engine is getting older and develops more blowby, maybe you run a different oil then before?
Different climate?
Steep inclines of camber and lots of throttle are typically causing this.

Eco tune will run leaner which is not always good but should not have caused this.

Thank you, going to install a catch can if for no other reason to keep the filter from getting covered and dripping out the vent holes all over the frame. It was just odd that it would go from never any oil to what I consider a lot in the course of one day (we check and blow out the filter after each day of trails) I do think the frequent downshifting of the trans causing high rpm and potentially very low vacuum may be the largest contributors (going to try and hook a vacuum gauge into the system and go for a drive as another bit of data). I would expect for a much larger pressure drop on the leak down test to result in that much blow by.

 

[smritte]

Oil in the intake (airbox, intake tube...) is a sign that the PCV system is not clearing the blowby gasses from the engine. This doesn't mean the new pvc is not working but more on the lines of its not able to keep up.

Under load, compression raises, whatever gases push past the rings end up in the crank case. These gases push past the pcv into the intake manifold.
Some piston designs do a better job of sealing than others, some PCV systems do a better job of scavenging gasses.
You only really have two possibilities. Rings not sealing or an issue with the PCV system. Some vehicle designs, have this issue from new. This is due to poor engineering.
If your PCV is working but cant keep up, the inside of your intake manifold is going to be a mess. BTW what's your oil consumption?

Leak down tests work to a degree. Remember, the pressure in your cylinder is between 100-150 psi before ignition. Blow by happens normally under a load, when combustion pressure is higher. A leak down will show a failure but if you had a failure, you would have other symptoms.
If I had a choice of running a catch can as opposed to getting oil into my intake manifold and ruining my EGR and or clogging everything, I would run one temporarily until I resealed or rebuilt my motor.

On another note, my 04 TJ PVC system was horrible. the design was poor and couldn't keep up with what the engine produced. I first noticed oil in my air box at 20k miles. I modified the PCV and didn't have the issue anymore. All the Jeep people I talked to said it was normal and just live with it. It was also suggested I run a catch can if It bothered me. My 180k miles Cruiser had the same issue as well as oil consumption. Everyone told me I couldn't fix it and just live with it. I rebuilt the motor and now I don't have the problem. Both of those vehicles passed a leak down with the TJ being perfect.

Over the years, I have seen what high blowby does to engines. Some people accept it. I choose not to.

 

[OTH Overland]

Oil in the intake (airbox, intake tube...) is a sign that the PCV system is not clearing the blowby gasses from the engine. This doesn't mean the new pvc is not working but more on the lines of its not able to keep up.

Under load, compression raises, whatever gases push past the rings end up in the crank case. These gases push past the pcv into the intake manifold.
Some piston designs do a better job of sealing than others, some PCV systems do a better job of scavenging gasses.
You only really have two possibilities. Rings not sealing or an issue with the PCV system. Some vehicle designs, have this issue from new. This is due to poor engineering.
If your PCV is working but cant keep up, the inside of your intake manifold is going to be a mess. BTW what's your oil consumption?

Leak down tests work to a degree. Remember, the pressure in your cylinder is between 100-150 psi before ignition. Blow by happens normally under a load, when combustion pressure is higher. A leak down will show a failure but if you had a failure, you would have other symptoms.
If I had a choice of running a catch can as opposed to getting oil into my intake manifold and ruining my EGR and or clogging everything, I would run one temporarily until I resealed or rebuilt my motor.

On another note, my 04 TJ PVC system was horrible. the design was poor and couldn't keep up with what the engine produced. I first noticed oil in my air box at 20k miles. I modified the PCV and didn't have the issue anymore. All the Jeep people I talked to said it was normal and just live with it. It was also suggested I run a catch can if It bothered me. My 180k miles Cruiser had the same issue as well as oil consumption. Everyone told me I couldn't fix it and just live with it. I rebuilt the motor and now I don't have the problem. Both of those vehicles passed a leak down with the TJ being perfect.

Over the years, I have seen what high blowby does to engines. Some people accept it. I choose not to.

Went through a bit less than 1 quart in 4k miles. Agreed, I am not one to simply put up with the old it's a Jeep thing or "they all do it". Funny enough it seems like the throttle body is not getting much oil from the PCV line, its all getting blown back into the airbox from the intake vent hose leading from the other head, leading me to think its a path of least resistance (or lack of vacuum to draw fresh air in). my other Jeep a WJ with a 4.7 has 240k on it, never had the engine open and it has zero blowby and does not use any oil between changes. do not think I want to rebuild the V6 with its marginal power, poor gas mileage, and high rpms. scales are tipping toward a hemi swap.

 

[smritte]

Funny enough it seems like the throttle body is not getting much oil from the PCV line, its all getting blown back into the airbox from the intake vent hose leading from the other head, leading me to think its a path of least resistance (or lack of vacuum to draw fresh air in)

Remember, Vacuum has very little to do with it if you have a check ball type PCV (there is still some flow but very little). The system works by having the intake lower pressure then atmosphere. During acceleration or higher load, intake vacuum is very slight but still lower than atmosphere. It's suppose to flow path of least resistance which is also suppose to be the intake manifold. If your producing more blowby than it can scavenge then yes, you end up with some in your air cleaner. I do find it odd that that when you replaced the PCV you didn't see any excess oil. On my TJ I had a ton of oil in the intake. The system was the metered orifice type. This is why it was normal to eat oil, clog things and end up with some in the air box. I switched to a check ball type and the issue stopped.


Where does your jeep pick up its fresh air from. My TJ was the intake tube. I switched it to the air box and got it out of the intake airstream. That mod can make you fail smog on a visual. On mine I would reattach it to the intake tube then put it back after smog.

 

[MazeVX]

I don't know exactly why it happens with the 3,6 but I have seen a lot of videos with jks on a trail doing funny clouds while processing huge amounts of condensate (jeah its not really oil) after some complicated obstacles...
I probably would have been nervous as well but in this case it seems like it's not an unusual thing to happen and they catch a lot in their catchcans, it's just mysterious that it happened suddenly

 

[zgfiredude]

So is a check valve style pcv in the "non-valved" line to the airbox a possible solution? I have read some info on catch can installs where they were only getting oil from this left side ( originally they installed dual catch cans ).

 

[smritte]

That isn't a bad idea but I wouldn't use a PCV because their a weighted ball. on my trailer I have a drain hose for my water tank. I put a 3/8 check valve inline to keep bugs from crawling up. Something in a 1/2 inch (12mm for the metric people) size would work well. Now we need someone to test this.

 

[OTH Overland]

Where does your jeep pick up its fresh air from. My TJ was the intake tube. I switched it to the air box and got it out of the intake airstream. That mod can make you fail smog on a visual. On mine I would reattach it to the intake tube then put it back after smog.

Fortunately we do not have smog testing anymore in Washington. The JK has a pvc valve at the rear of the right cylinder head that runs to the air intake behind the valve body, there is a second line serving as a filtered intake running from the airbox to the left rear cylinder head, All the catch cans systems go into the line from pcv to air intake, I am thinking of adding one to the intake tube before the airbox at least as a stopgap.

 

[OTH Overland]

That isn't a bad idea but I wouldn't use a PCV because their a weighted ball. on my trailer I have a drain hose for my water tank. I put a 3/8 check valve inline to keep bugs from crawling up. Something in a 1/2 inch (12mm for the metric people) size would work well. Now we need someone to test this.

I thought about a check valve, but figured if it was constantly dripping oil the line would be full and not work as an inlet at all, unless the oil only happens during hard acceleration and would then clear itself back into the engine on normal cruising. Might be worth an experiment

 

[Dilldog]

100 psi compression is quite low. For reference 70psi is the minimum required for combustion. A quick Google search shows 132psi as the service limit, so at 100psi, you should be planning a rebuild. So there's your answer, low compression causing excessive blowby.
As far as the oil in the air box goes, I would not try to block off the breather lines in anyway including check valves. That would probably cause main seals to blow as there's nowhere for the pressure to go.
Have you tried oiling the cylinders and redoing a compression test? If the numbers come up then it's a cylinder/ piston issue, if the numbers stay the same then its valve/ head issue.
Edit to add: how long did you crank the engine during the compression test? Did you continue cranking until the gauge stopped jumping and was steady? Did you hold the throttle wide open? After re reading your post I'm wondering if perhaps there was a simple mistake made during the compression check that is giving you an artificially low number...

 

[OTH Overland]

Don't think the throttle was it as the intake plenum has to come off on the 3.6 to get the plugs out of the left head so its wide open. Pretty sure the valves are sealing well, no sign of air leakage thru tailpipe or intake during leak down test, and 2% drop usually a good sign of ring sealing, valves, and head gasket. engine runs great, super quiet, responsive etc. only thing is gutless but jeep is way to heavy, and oil in air filter. would not expect any major issues on a 120k engine that has been well maintained since new. running out of ideas though unless something in the left head is causing oil to not drain back down fast enough and backing up into the crankcase inlet from the air box. going to see if i can find room for a catch can that way i can quantify how much is going into the filter.

 

[Dilldog]

So the intake runners were open allowing maximum air into the cylinders correct? What about cranking duration and pressure gauge behavior? Did you crank the engine until the needle on the gauge "stalled" at the highest reading? Maybe test again with a different gauge? Sorry but that 100PSI compression test really bothers me, I'm sure you couldn't tell, lol.

So just kinda thinking out loud here...
- Compression test low. However, they did come up consistent suggesting uniform engine wear so a failure would be unlikely
- Leak down test results in 2% loss, we can therefore say the combustion chambers are OK
- Engine power seems good, however there was a single event of decreased power
- Oil consumption?
- Fuel millage is still within expected range
Did I miss anything?

We may need to just take a step WAY back and get really basic.

The concern is oil in the air box, there is one of two breathers that joins the intake stream near the air box, this is where the oil should be coming from.
I kinda want to say the other breather is plugged or restricted causing an increase in crank case pressure thus forcing excessive oil vapor through the other line. Whether it be the PCV valve or the hose that connects to it, or potentially the port where the PCV valve fits into the engine (or where the hose connects to the intake/ throttle body) and if there is a baffle to help block oil spray from getting to the valve one of those may be restricted so they should all be thoroughly inspected. New engines run so tight on stuff like this for emissions so it may not take much to cause issues.

Also, just a thought, get an oil analysis done, just to see if there is something out of left field that contamination in the oil could help discover. Having been a mechanic for 10 years of my life professionally and privately for 20 years, this is the kind of issue that keeps me up at night, and these types of things usually turn out to be something crazy simple.

To Add: millage is something I stopped relying on as a troubleshooting aid (unless using it to reference duration since a previous inspection/ repair to gauge how bad an issue is). I have seen engines fail at 20K when they should have gone for 1,250,000, and the owners swear it was maintained well. Something as simple as using the wrong type of oil (the new Pentastar engines require a full synthetic I know, and 5w20 weight if memory serves), or a budget filter can kill and engine before its time.

 

[zgfiredude]

I like the "try a different gauge" theory.......they WERE all similar at 100 psi, but was it really 100 psi? As simple as a bad gauge that's reading incorrectly?

Doesn't address the oil in the filter concern, but it kinda is the "smoking gun" at the moment.

 

[OTH Overland]

So the intake runners were open allowing maximum air into the cylinders correct? Yes. What about cranking duration and pressure gauge behavior? Cranked until stable, gauge increased with each rotation, probably 3 or 4 compression cycles. Did you crank the engine until the needle on the gauge "stalled" at the highest reading? Maybe test again with a different gauge? Sorry but that 100PSI compression test really bothers me, I'm sure you couldn't tell, lol.

So just kinda thinking out loud here...
- Compression test low. However, they did come up consistent suggesting uniform engine wear so a failure would be unlikely
- Leak down test results in 2% loss, we can therefore say the combustion chambers are OK
- Engine power seems good, however there was a single event of decreased power For the most part, It started on our Thanksgiving trip to Death Valley, while pulling a pass at 6,500 pounds at about 90 percent throttle, the engine suddenly seemed to derate, and there was a noise that could be described as a logoff valve sound, limped to top of pass, then seemed pretty much ok. it was about 800 miles later Michelle noticed oil on the frame under the air filter box. now it seems the engine runs fantastic until accelerating around 5k rpm then its like it hits the rev limiter but we are below that.
- Oil consumption? Prior to oil in box, no oil added between changes, latest trip to Montana a bit less than a quart in 2k miles, hoping to get a catch can in to quantify amount of oil going to filter as there is a drain hole in bottom of box so do not really know how much is getting in there besides soaking lower end of filter.
- Fuel millage is still within expected range Fuel mileage is around 14-15mpg at 65mph. (Before we took our Thanksgiving trip I loaded a fuel economy tune from the Superchips programmer, Thinking about putting it back to stock, or one level up and see if that makes any difference.)
Did I miss anything? i do not think so, the previous owner was a collector of rare BMW on other cars, and had the Jeep serviced at the same dealer on schedule since they bought it new, lived in the garage and I got it with all records and had only one off road experience before we got it 14 months ago.

We may need to just take a step WAY back and get really basic.

The concern is oil in the air box, there is one of two breathers that joins the intake stream near the air box, this is where the oil should be coming from.
I kinda want to say the other breather is plugged or restricted causing an increase in crank case pressure thus forcing excessive oil vapor through the other line. Whether it be the PCV valve or the hose that connects to it, or potentially the port where the PCV valve fits into the engine (or where the hose connects to the intake/ throttle body) and if there is a baffle to help block oil spray from getting to the valve one of those may be restricted so they should all be thoroughly inspected. New engines run so tight on stuff like this for emissions so it may not take much to cause issues. After Thanksgiving, I pulled the intake, plugs and did the testing, plugs all looked good (had just replaced them when I purchased the Jeep), replaced the PCV valve located on the right rear valve cover (what a pain), old valve seemed to be in good condition replaced it anyway. blew some air through the two hoses (PCV to air intake, and Left cylinder head vent to air box) found nothing. reassembled and still an issue

Also, just a thought, get an oil analysis done, just to see if there is something out of left field that contamination in the oil could help discover. Having been a mechanic for 10 years of my life professionally and privately for 20 years, this is the kind of issue that keeps me up at night, and these types of things usually turn out to be something crazy simple.

To Add: millage is something I stopped relying on as a troubleshooting aid (unless using it to reference duration since a previous inspection/ repair to gauge how bad an issue is). I have seen engines fail at 20K when they should have gone for 1,250,000, and the owners swear it was maintained well. Something as simple as using the wrong type of oil (the new Pentastar engines require a full synthetic I know, and 5w20 weight if memory serves), or a budget filter can kill and engine before its time.

Was worried about the gauge also, pressure tested it with a compressor and a known gauge, right on par. I was expecting more like 140 psi. (Engine had been parked for a couple of days and was cold, did not try squirting any oil down the bores to see if it improved anything)

Other items:
- Added a bunch of overlanding jewelry over the past year, and a 3 inch lift with 35's (Reprogrammed speedo)
- Early November had Northridge 4x4 re-gear the axles to 4.88 (Reprogramed ECU for new gear ration (This seemed to help with power a bit, however the transmission seemed to be holding onto lower gears way to long around town and on hills. slightest hill caused trans to drop from 5th to 3rd. (5th to 4th not so bad increases rpm about 500 ish) (4th to 3rd is a huge jump of around 1,500 rpm)
- Mid December added a custom programmed TCM. This seems to have helped with daily driving, shifts much smoother and at lower rpm, has not helped much with hills and mountain driving.

Just pulled the hose of the air box yesterday and had Michelle run the Jeep through various RPMs and there is always a slight suction on the end of the hose, but not sure if that is overcome by the pull of the throttle body, (took a mostly level cruise to the coast and back in between our two longer trips where the average RPM was much lower and there was only a few drops of oil in the box, so perhaps the leakage is RPM or engine load sensitive)

Have WAY too much into the Jeep with purchase and the build to get rid of it and we Love it except for the current issue and the leaky doors lol . Not going to live with its a Jeep thing, will find a way to fix it...

I know the valves are sealing, and just can't figure if the rings were that bad to loose that much compression, how it only loses 2% on a leak down, nothing I have run into before.

Probably going to have to give up and take it in somewhere, just not sure where, have not had the best of luck at the dealerships, if it does not throw a code, they just seem to throw parts at it. Hate to just throw a new motor in it and find out it was something stupid. Michelle is of the opinion that if the motor is bad, and its already gutless, it might need two more cylinders... not a cheap option .

Thanks for the detailed reply and ideas, much appreciated.

 

[smritte]

Probably going to have to give up and take it in somewhere, just not sure where, have not had the best of luck at the dealerships, if it does not throw a code, they just seem to throw parts at it. Hate to just throw a new motor in it and find out it was something stupid. Michelle is of the opinion that if the motor is bad, and its already gutless, it might need two more cylinders... not a cheap option .

I'll give you some insight about dealers. I worked as a dealer tech from 79-06 then I became a trainer for a manufacture.
The dealer is the place to go with your low milage, less than five year old car. Dealer tech's have the "opportunity" for better training and have access to better information. Jeep techs, chevy techs,..... will have seen nothing but low milage vehicles for the time they spent there. At the end of the day it all boils down to the person. "IF" your vehicle is lucky enough to be assigned to someone who has seen this issue many times before, you have a chance that it will be diagnosed properly.
Your bigger issue will be a non dealer who, odds are will have never seen your issue in your vehicle type. Their diagnostic will be new motor.
If I worked at Jeep and you brought me your vehicle, I ("ME" because i'm OCD about things) would see what piston/ring design you have and still most likely put an engine in it anyway. The main reason is, at 100k seals start to fail as well as a number of surrounding engine parts. If I just reringed it, I would have to guarantee nothing engine wise will wear out within 1 year. I have seen engine jobs come back because the transmission started having issues two years later on a high milage car. The customer believed It was our fault because we were the last ones to touch the car.

Where ever you go, their going to look at the milage, see the mods (which put more load on the engine) and recommend a rebuild. If you haven't done it already (im sure you have) search out your issue with google and see what you find. You appear to be skilled enough already to come to the conclusions you have. As for your comment on low power, look at the bore/stroke/tune on that motor. Its actually designed for a somewhat lighter commuting vehicle.
I have a feeling with your knowledge, your going to end up with a motor swap.

 

[Dilldog]

Unfortunately most light duty shops have a tendency to throw parts as they work flat rate, wich should be illegal in my opinion. They only get paid if they make time on the job, being honest, a job like what you have will be impossible to make time for. This is why they will just tell you to toss a new engine in, especially with a 100psi compression test.

If you are getting some vacuum on the line that goes into the air box that is good, but when the engine is under load that may change. Do you have a way to plumb in a pressure gauge that will hold a reading into that line, go pull a big hill (or otherwise run the engine hard) for a bit to see if there is ever and pressure in the line? If pressure ever exists in that line it could indicate an issue with the PCV, and would potentially allow oil to run up that line and into the filter.

I will disagree with @smritte here, at 110K, there is no reason a modern engine should have any noticable wear. Even modern light duty engines are built to and regularly do go to 300K+. I know the Pentastars dont have the best reputation compared to others, but I would be surprised if there was enough wear at 110K to warrant an overhaul/ engine swing without investigating and finding a major issue.

 

[smritte]

there is no reason a modern engine should have any noticable wear.

I agree with that, there is not suppose to be a reason they still wear out, unfortunately it's not reality. I will say vehicles are way better then they use to be. The 70's -80's we would see leaking rear mains at 12k. 90's -2000's weren't as bad but it wasn't uncommon to start seeing leaks at 75k. I would really love to tear down an engine at 150 and see no noticeable wear. I will admit, the newest engine I've torn down was an 09 with the last Jeep motor being an 04. Aside from closer tolerances with the crank and rods, the seals haven't evolved. We still build pumps the same, tensioners are still plastic, chain design is the same its been for 40 years.
If you really want to see how a high milage vehicle is holding up, do oil samples. I send a sample out on all of my vehicles about every two years. Now you see what's really happening inside.
The OP is also not the original owner. Who knows what kind of treatment it got before.