oil leak in airbox - JeepForum.com
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post #1 of 5 Old 08-13-2019, 03:18 PM Thread Starter
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oil leak in airbox

So I recently bought my first Jeep, a 1991 Cherokee Laredo. It has 158,000 miles and since purchasing it I’ve redone the entire cooling system, literally the first day driving it where it didn’t overheat, I noticed an oil puddle under the vehicle, it seems oil is being sucked into the airbox. I’ve read a few threads about this exact issue, but can’t really find a detailed troubleshooting list. Any and all help is appreciated. One thing to note is that I’m not entirely sure how well taken care of this Jeep was. I don’t think the owners totally trashed it, but I don’t think they were as meticulous as I would’ve been.

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post #2 of 5 Old 08-13-2019, 03:34 PM
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excess blow by could also be an issue bu t check the PCV (CCV) system first...

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 5 Old 08-14-2019, 06:20 AM
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To understand the problem, the CCV system pull air from the airbox. If the balance of the system go out of wack the airbox pulls the air from the valve cover into it. I had this issue with my '88 Comanche. Try a new valve cover gasket. I like the molded FelPro one. Not cheap though $40. A few upgrades could help. Latter XJ's had a larger CCV Tube to the manifold. You need the fitting going into the manifold and the tube. Also, the 93-95 Grand Cherokee had an aluminum valve cover with the newer grommets, CCV port meters. Don't know if it works better or not.
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post #4 of 5 Old 08-14-2019, 11:40 AM
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The CCV system needs to be set up right.


Here are the parts you need.


Rear Elbow (low flow) Identical to what I pulled out

Front Elbow (high flow)

Amazon says it does not fit but it does.

Everything fit in nice and snug.
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post #5 of 5 Old 08-16-2019, 07:57 AM
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This helps also:

Most early and even later Renix 4.0s could be bothered by excessive oil in the air cleaner box.

A fix from my old days as Service Manager at a Jeep dealership follows. Information was provided to me from a buddy at JeepTech during those days. I don’t believe it ever came out in a Technical Service Bulletin.

Remove the valve cover and turn it over. Next, remove the fluted tubes that are now facing you by removing three screws on each.

Valve cover flute

Chop 1 inch off each of them. Then, drill a half inch hole as shown in the photo. The flat side of the flute that’s closest to the edge of the valve cover. valve cover flutes (2)

Clean and de-burr/sand all rough edges nicely, clean with solvent, and reinstall. Don’t be concerned about the chintzy gaskets that will probably crumble into oblivion when you remove the fluted tubes. They can go back together without gaskets.

For photos and video, click here: http://cruiser54.com/?p=131

If you own a Renix Jeep, you must check this out:

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