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Old 01-05-2014, 12:32 AM   #1
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I've been looking this one up for a while and I'm confused. I've got oil coming into the air box and contaminating my air filter from a hose that comes out the top rear of my valve cover (1991 YJ 2.5l 4 cyl). It only does it when I've been at sustained highway speeds for a while. There's also a hose that comes out of the front right of the valve cover and goes directly into the throttle body.

I was told to replace my pcv valve and I got one but it doesn't fit. It's the one that matches my engine at an out parts store but does not match the hole on the too rear of my valve cover. It looks like this…Name:  image-3045222523.jpg
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The one this is currently in my jeep attached to the top rear of the valve cover and goes into the air box hose looks exactly like this and is hollow. Should it be hollow?Name:  image-3432217006.jpg
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Old 01-05-2014, 01:20 AM   #2
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I've been looking this one up for a while and I'm confused. I've got oil coming into the air box and contaminating my air filter from a hose that comes out the top rear of my valve cover (1991 YJ 2.5l 4 cyl). It only does it when I've been at sustained highway speeds for a while. There's also a hose that comes out of the front right of the valve cover and goes directly into the throttle body.

I was told to replace my pcv valve and I got one but it doesn't fit. It's the one that matches my engine at an out parts store but does not match the hole on the too rear of my valve cover. It looks like this…

The one this is currently in my jeep attached to the top rear of the valve cover and goes into the air box hose looks exactly like this and is hollow. Should it be hollow?
Yes its hollow. Read this in my manual last week. The rear hose is actually a vent hose. I messed mine and had to replace the rubber gourmet and plastic piece last week because I thought it was a PCV. The front is the CCV (crankcase ventilation). It does the same as a PCV. No idea why they changed it.. My 94 2.5 does the same thing with the oil in the air box, not to the point that it gets on the air filter though. Maybe someone else can answer that.

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Old 01-05-2014, 08:42 AM   #3
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I had the same problem with my ‘94 2.5. It would burp a wee bit of condensed oil vapor at start up thru the rear vent line into the air filter. It also had the slightest stumble just off idle. While doing the valve cover gasket 2 weeks ago I was cleaning the cover in the tub I noticed not much flow through the ccv fitting (front of cover). I pulled the fitting off and found the hole in the valve cover 95% plugged. After cleaning, reassembly and test driving not only was the oil leak fixed but my off the line stumble and oil in air filter resolved as well.
It’s easy enough to check with the cover in place but I would recommend pulling the cover to clean it out so as not to have any nastiness falling inside the motor.
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Old 01-05-2014, 09:16 AM   #4
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Like said above. My 94 4.0 is similar. It was puking oil in the filter need up the vac line was dry rotted and collapsed and it would burp oil to filter. I also pulled valve cover and cleaned it as that is also a problem with them 6k miles later no oil in filter.
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Old 01-05-2014, 11:59 AM   #5
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Clogged air filter will cause more suction for ccv
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Old 01-05-2014, 12:03 PM   #6
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Small brass metering fitting on manifold must be cleaned out periodically to follow hose to manifold..mine was clogged and then it sucks into air filter
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Old 01-05-2014, 03:53 PM   #7
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Small brass metering fitting on manifold must be cleaned out periodically to follow hose to manifold..mine was clogged and then it sucks into air filter
Manifold? I'm assuming throttle? Or exhaust manifold? I'm still kind if a noob when it comes to some engine stuff.
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Old 01-05-2014, 04:01 PM   #8
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Follow hose from rear valve cover to manifold.upon removing hose at manifold you should see a screw in brass fitting..remove fitting .theres a very small hole in it that can clog up thereby crank case ventilation comes out other hose to air box
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Old 01-05-2014, 04:17 PM   #9
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Sorry my bad is on front hose on 2.5 at valve cover
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Old 01-05-2014, 04:18 PM   #10
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Trying to put on a pic in service manual for you
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Old 01-05-2014, 04:29 PM   #11
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Here's a pic
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Old 01-05-2014, 04:29 PM   #12
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The 2.5 and 4.2 vents into the air box/cleaner. On a 4.2 there's an "element" that catches most of the oil which should be changed at least when a tune up is done on a stock set up. It's actually normal. The PCV is for the front on both engines.
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Old 01-05-2014, 04:30 PM   #13
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Ok thanks. I follow you on where to follow the hose. I'll check it out when I'm back at my brothers again. I left my service manual 250 miles away at my place, of course I would :/
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Old 01-05-2014, 04:59 PM   #14
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I used a compressor water collector from harbor freight,Were the hose loops down is we're I installed mine. Also the bottom part unscrew to empty every so often
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Old 01-05-2014, 05:26 PM   #15
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I used a compressor water collector from harbor freight,Were the hose loops down is we're I installed mine. Also the bottom part unscrew to empty every so often
"racer" guys call it an "oil catch can". One can easily be made from PVC or I have even seen a Jim beam bottle.
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Old 01-05-2014, 05:41 PM   #16
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Trying to put on a pic in service manual for you
Is this the fitting

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that needs to be cleaned every so often
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Old 01-05-2014, 06:13 PM   #17
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Yes it is .screws into valve cover
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Old 01-05-2014, 06:44 PM   #18
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Logitech, I like that idea!
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Old 01-07-2014, 08:31 PM   #19
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Instead of replacing the hollow elbow on the rear of the valve cover could you replace it with one of those small cone air filters
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Old 01-09-2014, 07:12 AM   #20
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I had a breather on mine. clogged with oil in a week. I so need a new engine..
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Old 01-09-2014, 08:32 AM   #21
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Do a compression check to see if your rings are worn
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Old 01-09-2014, 09:27 AM   #22
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Instead of replacing the hollow elbow on the rear of the valve cover could you replace it with one of those small cone air filters
Bad idea. That essentially creates an air leak. In the stock setup, you have a vacuum on both sides of the valve cover. Only use a breather if you eliminate the PCV. You will pull fresh air through the breather, into the crankcase, and then into the throttle body. Possibly pulling more oil with it.

PCV/CCV = (Positive) CrankCase Ventilation. This is to meant to burn blow-by gases from the cylinders in the crankcase instead of venting them to the atmosphere. The PCV valve is a check valve meant to close when intake vacuum drops, usually under load (low rpm and open throttle). In addition to the PCV valve you will typically have a "balancing vent" that also goes to a vacuum source commonly at the air filter housing after the filter. In the picture of the manual page, the balancing vent is labeled "air inlet". The balancing tube will keep the engine from having too much vacuum in the crankcase.

To test your pcv is working correctly, pull the oil cap while the engine is running. A sheet of paper over the hole should stick just enough to give some resistance when you pull it away. if it comes off with no resistance, then something is plugged. If it blows off, then you have excessive blow-by.
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Old 01-09-2014, 10:34 AM   #23
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To test your pcv is working correctly, pull the oil cap while the engine is running. A sheet of paper over the hole should stick just enough to give some resistance when you pull it away. if it comes off with no resistance, then something is plugged. If it blows off, then you have excessive blow-by.
I take it something is wrong then. I opened the oil cap and remembered a while back that air was blowing out of the oil cap at me. Worn piston rings? I'll get the compression checked soon.
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Old 01-09-2014, 11:16 PM   #24
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Shortly after I replaced the elbow, my engine started leaking oil bad and getting all over the passenger fender. Turns out the plastic elbow had a small inlet hole, so I drilled it as big as possible. So far no more oil leak, but I still need to clean the CCV.
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Old 01-10-2014, 05:10 AM   #25
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Bad idea. That essentially creates an air leak. In the stock setup, you have a vacuum on both sides of the valve cover. Only use a breather if you eliminate the PCV. You will pull fresh air through the breather, into the crankcase, and then into the throttle body. Possibly pulling more oil with it.

PCV/CCV = (Positive) CrankCase Ventilation. This is to meant to burn blow-by gases from the cylinders in the crankcase instead of venting them to the atmosphere. The PCV valve is a check valve meant to close when intake vacuum drops, usually under load (low rpm and open throttle). In addition to the PCV valve you will typically have a "balancing vent" that also goes to a vacuum source commonly at the air filter housing after the filter. In the picture of the manual page, the balancing vent is labeled "air inlet". The balancing tube will keep the engine from having too much vacuum in the crankcase.

To test your pcv is working correctly, pull the oil cap while the engine is running. A sheet of paper over the hole should stick just enough to give some resistance when you pull it away. if it comes off with no resistance, then something is plugged. If it blows off, then you have excessive blow-by.
I cleaned the ccv tube and just removed and cleaned where the elbow went (broke the elbow of it was so cold and brittle) but I replaced the grommet and the elbow with a breather for now I guess and changed the gasket it was all clogged with grossness so I guess I need to get the elbow again thank you
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Old 01-11-2014, 02:28 AM   #26
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When you cleaned the CCV did you have one of these plastic pieces in the hose that is attached to the value cover. What is it for.

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Old 01-11-2014, 03:09 AM   #27
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When you cleaned the CCV did you have one of these plastic pieces in the hose that is attached to the value cover. What is it for.
I haven't touched the ccv valve yet at all (assuming you mean the one that comes out of the front right side of the valve cover when standing in front of the Jeep when facing it).
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Old 01-16-2014, 01:42 PM   #28
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When you cleaned the CCV did you have one of these plastic pieces in the hose that is attached to the value cover. What is it for.
I didn't have that I'm not 100% positive what that is but the metal fitting that I unscrewed from the valve cover had a hole about that size I used a piece of wire to clean it out and then sprayed inside the hole with brake clean

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