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Where is this oil coming from?

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According to the PO, it's known that the RMS and T/C have been leaking a few drips since I purchased the Comanche, but it seems to be a lot worse now, and I'm not entirely sure that it's all from the RMS (though, it might be contributing), but not sure. At some point, it looks like the oil pan + gasket were replaced, as they're definitely newer, and I don't think the PO completed that. If those were done, I would imagine the RMS was also done, so...


Oil accumulates under the drain plug. Where the RMS is is wet, along with the bolts on the oil pan on the passenger side. Looping around from the RMS to the driver side, it's dry.


Moving up further, the oil filter adapter is wet, and mostly everything around it is wet, too. I didn't snag a picture from down below, but kept moving upwards.


From the top end of the engine, you can see that there is oil around the oil filter adapter, and even above it, which I took some pictures of.




As you can (hopefully) see from the second picture, it's not the valve cover. It's wet up until that strap point holding that wiring harness.


I don't know how oil would get up that far, maybe just from leaking out from the oil filter adapter or oil pressure sending unit, and spraying upwards?


What do folks think?

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Oil filter adapter has a o-ring  that's common to leak. Which appears to be leaking. And just cause oil pan has been done dosent mean the rms was done. And the valve cover can always be doubled checked for tightness as the rear bolts are known to loosen up. 

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A couple years ago, I replaced all the seals for that oil filter adapter because I had the same oil leak.  I even tightened up my head bolts to try to address it, thinking the leak was originating from that head/block mating point.  It's still not bone dry along the side of the block today, but between those two attempts I believe I did make a bit of a difference.  


By the way, I also replaced the valve cover gasket with a premium, reusable (and expensive) one.  Like you, it really just didn't look like the leak originated up that high, but what the hell I bought that gasket anyhow figuring it was a nice upgrade for what may be more frequent valve cover pulls.


Looking forward to hearing what you eventually come up with.


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Found this: http://www.lunghd.com/Tech_Articles/Engine/Oil_Filter_Mount_O-Rings.htm which has some good info. Although, I'm fairly certain mine has a hex head and not a Torx like mentioned. I guess does that mean I would need the Renix or HO o-rings?


"Again: Get the correct o-rings for your mount! If your filter mount uses the Torx style bolt you will need the 'kit'; if you use a box-wrench to remove the center bolt you'll have to get the o-rings seperately and they MUST be the correct size!"

I'm guessing this kit will cover me: https://www.oreillyauto.com/detail/c/dorman-help/engine-cooling/engine-oil-cooler-seal/1fafab18ecda/dorman-help-oil-adapter-gasket-assortment/mtm0/82560

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Ran out and picked up some o-rings, replaced them, put it back together, aaaaaand--she's not starting. Makes 0 sense, unless this ugly no-start issue just seemingly happened to pop up at the same time... WTF 



What's interesting is my o-rings were the Renix-era ones, even though the threads on the adapter are standard (using WIX 51515 filter). Weird.

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I’d be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF.

Everybody, who doesn’t own or have to pay for or perform your vehicle repairs, loves to poke their noggin UNDER the Jeep and come out bearing the false bad news that your RMS is leaking. Many mechanics, friends, and good old Uncle Bob seem to enjoy telling you it’s the rear main seal. Has a catastrophic ring to it, doesn’t it?

A simple leak at the back of the valve cover or other source could produce the same symptoms. You don’t need to be a mechanic to figure this out. If you have good eyesight and a dim flashlight, you’re good to go on your own. Don’t jump on the RMS/oil pan gasket bandwagon right off the bat.

Almost any oil leak on your 4.0 is gonna drip from the RMS area for two simple reasons:

First off, the engine sits nose-up and any oil will run back to the RMS area.

Secondly, the RMS area is also the lowest point on the engine. Simple physics and the old plumber’s adage apply here: “Crap flows downhill”.

Valve cover gasket, oil pressure sending unit, oil filter adapter seals and distributor gasket, in that order, have to be eliminated as possibilities first.  A little tip here. Rather than use a dizzy gasket, use an o ring instead. NAPA #727-2024. Tips 12 and 13 will help you get your distributor back in place correctly. 


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Went back out this morning, only a couple drops on the ground. Oil still accumulating under the drain plug, and underneath the metal strap where the oil pan dips/where the RMS is. Definitely no longer leaking from the oil filter adapter, so I guess that scratches that off the list.

Valve cover gasket looks dry all around, so will need to tackle the oil pressure sending unit and distributor gasket next.

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