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Typical oil in airbox

D

donnielovett

NAXJA Forum User
Location
Colorado
Alright so i got an 88 xj with a 4.0 as a project and before i start modifying it and building it im trying to fix a few small things one being all the oil leaks and one in particular i thought i solved. Its was getting oil in the air box so i eliminated the pcv completely and ordered and valve cover breather well just today went to check the oil level an noticed some oil on the top of the valve cover and pulled out the breather and the material inside was clearly wet with oil, and noticed i get a smell of oil fumes inside but it doesnt smell like burnt oil. The odometer reads 270,000 miles but the guy claims it was rebuilt, its debatable still runs good, a little slow but not sure on gearing either. Any suggestions why im getting so much oil coming out of the pcv side? Should i do a compression check? Or is there another fix?
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It's not clear where you're routing what was originally the vacuum side of the PCV system.

It's pretty hard to prevent any oil at all in the air box of older XJ's, but I found that with my old 87 it made more difference than you'd think to get the right, updated vacuum line. The original had sharp bends in it, and breathed badly. When that happens, excess fumes go backwards into the airbox. The later modification used gentler bends in the line, and when new and clean, this pulled enough fumes out so that the air inlet from the airbox to the front of the cover continued to run the right way.

Later engines use a slightly fatter vacuum line, and seem to work better, so I wonder if you might try getting a vacuum line from a later one. Whatever you use make sure that it's truly vacuum tight because it must actually pull a little negative pressure to get the fumes moving in the right direction.

You'll almost certainly get fumes out the breather, which is why the original system breathes through a closed line from the air box. A little oil is probably all right as long as it doesn't mess up the filter too much.

I also took the valve cover off my 87 and cleaned out as much of the coked-up crud on the deflectors as I could, and that also seemed to help. The whole system runs on what appears to be black magic, and depends on a mysterious balance of forces, part of which seems, in turn, to depend on the metal deflectors beneath the inlet and outlet of the cover being free of accumulated grunge. Be careful if you do this not to allow too much of the grunge to fall into the engine. There is likely to be a lot of loose crud in there.
 
Matthew Currie said:
It's not clear where you're routing what was originally the vacuum side of the PCV system.



It's pretty hard to prevent any oil at all in the air box of older XJ's, but I found that with my old 87 it made more difference than you'd think to get the right, updated vacuum line. The original had sharp bends in it, and breathed badly. When that happens, excess fumes go backwards into the airbox. The later modification used gentler bends in the line, and when new and clean, this pulled enough fumes out so that the air inlet from the airbox to the front of the cover continued to run the right way.



Later engines use a slightly fatter vacuum line, and seem to work better, so I wonder if you might try getting a vacuum line from a later one. Whatever you use make sure that it's truly vacuum tight because it must actually pull a little negative pressure to get the fumes moving in the right direction.



You'll almost certainly get fumes out the breather, which is why the original system breathes through a closed line from the air box. A little oil is probably all right as long as it doesn't mess up the filter too much.



I also took the valve cover off my 87 and cleaned out as much of the coked-up crud on the deflectors as I could, and that also seemed to help. The whole system runs on what appears to be black magic, and depends on a mysterious balance of forces, part of which seems, in turn, to depend on the metal deflectors beneath the inlet and outlet of the cover being free of accumulated grunge. Be careful if you do this not to allow too much of the grunge to fall into the engine. There is likely to be a lot of loose crud in there.
Click to expand...


Ill have to look into that i know i have a leak at the valve cover gasket so i have to pull the cover anyway but its seemed to push alot of oil out of that hole in the few short drives ive driven it. (Maybe 20miles a week since i put in the breather a month ago)
 
donnielovett said:
Ill have to look into that i know i have a leak at the valve cover gasket so i have to pull the cover anyway but its seemed to push alot of oil out of that hole in the few short drives ive driven it. (Maybe 20miles a week since i put in the breather a month ago)
Click to expand...

See post 3 as you'll have the cover removed to replace the gasket. Be sure to use a Felpro blue gasket.

Never a bad idea to replace the rear vac line with grommet.

Napa 715-1365.
 
I would recommend running a can of BG44K through the fuel. It can help remove carbon and even help freeing up a stuck oil ring. It will also clean the injectors. Maybe a can of ATF in the oil a hundred miles before your next oil change. I might think about doing a compression and leak down test to see what shape things are in.

When you pull the valve cover, remove the baffles and clean out all the gunk. A new set of hoses was running around $20 for the complete harness.
 
I don't know about on here but, over on CF, there's a write-up for a valve cover mod that helps it breath better and helps to keep the oil out of the air box. I haven't done it yet but plan too soon, when I get ready to replace my seeping VC gasket.
 
I believe some have run an in-line filter between the VC and the airbox.
 
I run an oil/air separator in my PCV system. Plumbing wise, it sets between the rear elbow and the supercharger's intake manifold. I installed a Moroso part and it does a good job.
 
I hade the same issue on my moms 89 XJ and believe its causes by blowby aka.. bad piston ring or rings. Her jeep was getting tons of oil in the air filter and I did a mod I read about that has drastically lessened the amount of oil getting to the filter. What I did was remove the valve cover unbolted the two vent tubes inside it, cut about 1'' off each one and also drilled a hole in each of them and reinstalled and it helped a lot.
 
thanasi85 said:
I hade the same issue on my moms 89 XJ and believe its causes by blowby aka.. bad piston ring or rings. Her jeep was getting tons of oil in the air filter and I did a mod I read about that has drastically lessened the amount of oil getting to the filter. What I did was remove the valve cover unbolted the two vent tubes inside it, cut about 1'' off each one and also drilled a hole in each of them and reinstalled and it helped a lot.
Click to expand...

Yep. Search "cruiser's mostly Renix tips via Google. NAXJA does not host the tips for some reason......
 
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