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Discussion Starter · #1 ·
I keep getting this oil spatter from the aftermarket filter that was already there when I bought the YJ. Is this an issue?
 

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If you care about a clean engine then yes it is an issue... If you don't then no, not so much.
 

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Discussion Starter · #3 ·
If you care about a clean engine then yes it is an issue... If you don't then no, not so much.


Fair enough ;-). As long as it’s not a warning sign about worn valves or piston rings or some other serious issue.


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Your '94 2.5 probably has a CCV valve on the front of your valve cover. Sometimes it's mistakenly called a PCV.
If it isn't functioning properly (plugged or not connected properly) it can cause the oil spatter that you see.
The filter that you have allows clean air to enter the crankcase and the CCV regulates the flow of air out of the crankcase to be burnt during combustion.

If the CCV is properly connected and not plugged then you might have some blowby, indicating worn rings. If that's the case, I wouldn't worry about it. Just clean your engine and add a little oil as necessary and enjoy your new rig.

Most engines have some degree of blowby. As engines wear, blowby increases to the point that crankcase pressure (blowby) overwhelms the design of the CCV or PCV system and you get some "splatter" out of the air intake.
Older or high mileage vehicles are more prone to this and most of us simply live with it. It's just a fact of life.

On my 4.2 with almost 200K miles, when I drive around town, I get a little oil mist in my air cleaner. (Unlike OP, I have the stock setup, not an aftermarket filter).
When I drive long distances at highway speeds, my air filter gets oil saturated and I have to replace it. I usually carry a spare air filter and oil. Just a fact of life with old vehicles.

Good Luck, L.M.
 
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Discussion Starter · #6 ·
Well that doesn't sound good at all. I'm going to check the FSM and make sure they didn't screw something up before I got it (wouldn't be the first thing!). Thanks!
 

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Actually that filter is connected where the ccv should be
On some 4 cylinder engines I remember seeing a valve on the front drivers side of the valve cover. I was under the impression that that was the CCV. Not actually a valve, but a small orifice in a plastic or brass elbow.
I could be remembering a different year or an entirely different vehicle.

If that filter is where the CCV goes, where is the air inlet to the crankcase?
I guess I could find a post by Got it at last and look in his signature for the link to the Factory Service Manual for OP's Jeep. I'll leave that to OP though, since he needs to know about the CCV plumbing more than I do.
Look in the 2.5 engine section or the emissions section.

Good Luck, L.M.
 

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Discussion Starter · #8 ·
Checked the FSM and that is the correct location of the clean air intake for the 2.5L. Just need to make sure the vacuum pipe to the throttle body is clear now. Thanks guys!


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I could have sworn the line to the intake was on the back and line to air cleaner was on the front... oh well...
 

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No actually, the elbow with the filter on it is supposed to have a hose going to the airbox. The small connection on the front driver side goes to manifold below the throttle body.
 

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No actually, the elbow with the filter on it is supposed to have a hose going to the airbox. The small connection on the front driver side goes to manifold below the throttle body.
^^^This is how I remember the 4 cyl setup as being. I wouldn't worry about the filter or the elbow that's usually there being connected to the air box. Just as long as the crankcase can inhale filtered air.
That said, I would rather have everything as close to factory as possible unless I had a good reason for it to be different from factory. If OP has the factory air box, he might be able to return the crankcase air to original factory configuration. It's easier to wipe down the inside of the air box than clean the valve cover or the entire engine if he continues to get spatter.
Plus, it'll be easier to find a stock air filter at any small town parts store than to find a replacement filter that he currently has.

Good Luck, L.M.
 

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Checked the FSM and that is the correct location of the clean air intake for the 2.5L. Just need to make sure the vacuum pipe to the throttle body is clear now. Thanks guys!
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There should be a small opening somewhere in the fitting that attaches to the valve cover. If you can get the hose off easily, you might be able to poke the orifice with a round toothpick or similar instrument.
I haven't done this so I'm simply speculating.

Other posters with 2.5 engines that have cleaned or replaced their CCV should chime in.

Good Luck, L.M.
 

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Keep in mind the ventilation system(CCV) works off of engine vacuum. When you're running 5th gear against a head wind uphill and you have the throttle mashed down you have very little vacuum available to clear out the oil vapors so they start looking for the next easiest way out of the engine, which for you is that fresh air filter.
Just decide where you'd like that oil/moisture muck/vapor to go and you'll be all good.
 
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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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I could have sworn the line to the intake was on the back and line to air cleaner was on the front... oh well...
Just another dumb question, I guess I could see where on the 2.5 with the port out the side of the valve cover and the vent to the air cleaner out the top, that there may be some engineering aspect as to which goes where. But on the 4.0 and 4.2 sixes with both vents on top and the design of the valve cover, does it/would it, really make a difference which goes where??
 

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On the 4.2 I can't see where it makes any difference.
Same for the 4.0, but there may be something about the 4.0 setup that I'm not aware of.

Good Luck, L.M.
 

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Best I can remember both ends of a 4.0 valve cover are baffled the same...
 

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This is one of my late 4 cylinder YJ’s, which would be the same as yours jhendry. Poor pics, but in the first pic you can see the vacuum tube (where your little K&N style filter is) that goes to the air box, and the ported vacuum line from the vacuum harness at the front of the valve cover. The second pic is with the air box and tube removed.

I would never put a pleated air filter directly on an internal combustion engine that builds significant crankcase pressure, for obvious reasons. A remote breather, with or without a catch can, is something I have used often in HP engine builds. Different approach to the solving the inherent result of crankcase pressurization.
 

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