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oil in the the air box

F

Fozzy

NAXJA Forum User
Location
Lynnwood,WA
so i got the do some basic maintaince on my jeep teh other day and after changing oil moved onto the air filter, only top find the old filter soaked with oil. pretty sure this is a bad thing. took the head off to make sure oil was draining into the block and there was nothing clogging oil flow. anyone else expeience oil flowing into their air box?
 
Head or valve cover? There is a flapper valve in the top front of the valve cover under the hose leading to the airbox that gets gummed up. Easiest to clean with the cover off, but you can hose it off from above as well. Pull the little crankcase vent tube from the back of the valve cover and blow it out with carb cleaner. It tends to get plugged up and cause oil in the air filter.
 
Mine has that problem as well... its fairly normal for high mileage XJ's
 
I had the same problem. Do a search on 'Blow-by' as stated before. Also look at Mad-XJ for the big tube CCV update. I was using 1 quart in 100 miles or so. After getting a good valve cover seal and doing the 99+ CCV update on a Renix motor it didn't put oil in the airbox.
Tom
 
thanks for the info guys. it was the valve cover that i removed. i also cleaned that flapper gasket like thing while the cover was off. ill look into what you said about blow by and CCV.
 
Last edited:
Here's some more links:
www.off-road.com/jeep/cherokee/xjtech/engine/40ltr/blowby.htm
www.off-road.com/jeep/cherokee/98/04_apr/valvecover/cover.html
www.madxj.com/MADXJ/technical/technicalfiles/JAvalveCover/ValveCover.htm
http://www.yuccaman.com/jeep/filter.html
I didn't check them though. I did clean my valve cover and replaced all the hoses in that article. I still had 'blow-by'. I think the main cause is that the valve cover gasket or seal is leaking air into the system. Its to much for the CCV tube to handle. The airbox over powers the CCV tubes suction and sucks oil into the air filter. So, get a good valve cover seal. You might chack some of the new FelPro gaskets. I hear they make some rubber/cork ones. I didn't have much luck with pure cork ones. Also, it would help to know what year engine you have. Also, check NAPA for those CCV parts. I hear they can get them and cheaper than the dealer.
Tom
 
Try this for a cheap and easy fix. I did mine about 500 miles ago and havent had the problem since. Plus its a lot cheaper and easier to clean out than the plastic lines.
IMG_0047.jpg
 
I read all those threads about how to get the parts from the dealer to repair the OEM set up, but I've been thinking that I don't really need to do all that. I like mcnamaag's setup and think I'll copy it.

Does that hose have to be routed in to the airbox? Can I just route it to a can/jar/bottle or something to catch the oil rather than have it blow into the air filter? Why did it go into the air box anyway?

[Cool blue heater hose BTW.]
 
The hose to the airbox is suppose to suck air from the airbox. In your case the airflow is imbalanced or messed up. I think because of a clogged CCV tube and/or a leaking valve cover gasket. You could put one of those valve cover breather filters on the front hole. Look at the Ricer section in AutoZone or Advanced Auto. You still didn't specify the year. I had heard of someone useing the PVC gromment from a 258 Jeep vavlecover and the PVC valve on an 87-90 Renix valve cover. I put on a 91-95 4.0L valve cover and did the Mad-XJ big tube conversion.
Tom
 
Autozone can get the good felpro valve cover gasket with the metal surrounded by the buttel blue rubber. I went through 3 corks with little to no success in stopping the leaking of valve cover. I replaced the cork with the 50 dollar gasket and I haven't had a leak since then.
 
My jeep is an '87 if it helps. its from that hose that blue hose that the oil is entering teh air box. so im thinkin it's the CCV tube tahts clogged. ill keep an eye on teh leaking seal idea too.
 
Thanks guys.

75SV1 said:
The hose to the airbox is suppose to suck air from the airbox. In your case the airflow is imbalanced or messed up.
Click to expand...

So if I just route the hose to the ground and have it end below the engine so it doesn't spew oil on my motor (causing that buring oil smell) will that keep the airflow imbalanced? Does that cool blue hose still go to the airbox in the photo?

75SV1 said:
I think because of a clogged CCV tube and/or a leaking valve cover gasket.
Click to expand...

Surprisingly I don't think I have a leaking valve cover, but I'm blowing alot of oil through that hose.

75SV1 said:
You still didn't specify the year.
Click to expand...

Oh, we need signatures. I have an 88 XJ, I6, AW2, 231 TC. (I think that's the number of the TC.)
 
I have the very same problem. I also tried routing the larger hose to the ground just in front of my axle. Dont do it! When it comes time to clean the Jeep, you will be sorry! That oil that comes out, even though it is a relatively small amount, turns into one helluva mess when blown and spread by the airstream going under the Jeep.

Best solution is those suggested above. Either replace the valve cover gasket, clean the flapper and install a new CCV system or; repair/replace the engine so it doesnt have the severe blowby.
 
Tally_XJ said:
I have the very same problem. I also tried routing the larger hose to the ground just in front of my axle. Dont do it! When it comes time to clean the Jeep, you will be sorry! That oil that comes out, even though it is a relatively small amount, turns into one helluva mess when blown and spread by the airstream going under the Jeep.

Best solution is those suggested above. Either replace the valve cover gasket, clean the flapper and install a new CCV system or; repair/replace the engine so it doesnt have the severe blowby.
Click to expand...


Or a catch tank.....
 
im thnkin of riggin one of teh import brether filters onto teh hose as it enters teh airbox. this should take care of the small amount of oil gettign blown into there.
 
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