Oil Leak - Pretty Bad!

Hey guys, got one for ya. '94 XJ Sport, 4.0L HO, AX-15, NP231. Lost all oil pressure on the expressway yesterday, pulled off immediately and realized that I had zero oil in my crankcase. This is a motor that had blown a head gasket that I replaced, and done the MadXJ CCV setup which worked flawlessly.

I now have a leak somewhere in the rear of the motor - Rear Main, VC gasket, Head Gasket, Oil Pressure sender. . . any other ideas? And how to figure out each one? At this point it drips even when turned off, and I've got a puddle the size of a dinner plate underneath it from about 12 hours of sitting. Any ideas what to do from here?

Re: Oil Leak Woes

I have "Threads that end with Woes" woes.

Anyways matty, I reckon your rear main seal farted out on you. It's only a couple hundred to replace if you don't want to do it in your garage :[

Not a 'woes' thread no more!

yeah, I'm thinkin' it's rear main time. shouldn't be too bad, a project for tomorrow.

With a rear main leaking that bad your clutch would be giving you fits.

The rear of the valve cover is know to leak easly. Also I have seen oil pressure sending units leak.
Oil filter on tight?

langer1 said:

With a rear main leaking that bad your clutch would be giving you fits.

The rear of the valve cover is know to leak easly. Also I have seen oil pressure sending units leak.
Oil filter on tight?

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Haven't driven it much since it happened. I was babying it, and the clutch seemed fine.

I replaced the valve cover gasket, not head gasket. Seemed to seal up pretty well. The oil filter is on the way I usually install it - finger tight. There's actually oil that has dripped onto the top of the filter, but that's it. Somewhere on the back of the motor - VCG, head gasket are possibilities still. I have no idea where the oil pressure sender is. . . time to hit up the FSM.

Oil pressure sender is this cylinder that's plugged into the block near the oil filter with a wire hanging out the back. It's about the size of a shot glass.

RyleyF said:

Oil pressure sender is this cylinder that's plugged into the block near the oil filter with a wire hanging out the back. It's about the size of a shot glass.

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Ten four

Try tightening the valve cover bolts. This just happened to slowrider this past weekend. His MJ was spewing oil and he figured it was the rear main seal. But he tightened up the valve cover bolts and no more leak.

That's not to say that your rear main seal doesn't need replacing. But try tightening the bolts first.

If you have oil on the top of the oil filter, I'll bet it's the oil pressure sender that's leaking. Remove the electrical connector, and you'll see lots of oil inside. A new sender is about $21 at AutoZone. It's located directly above the oil filter.

My 96's sender is leaking too.
:repair:

langer1 said:

With a rear main leaking that bad your clutch would be giving you fits.

Click to expand...

I drove mine for over a year with a 1qt/200mi leak and never had any clutch problems. Disassembly during engine replacment showed no contamination to clutch or flywheel.

Just FYI

Rev

Well, here's the plan - just got off work, headin' over to the shop.

I acquired a new rear main seal and oil pan gasket - so I'm going to start with the rear main, tighten the valve cover (as I recall it was hell to try to get those back bolts tight without a really long extension, maybe I need to try again) and check the sender.

Will report in later, see if my baby runs better.

Interestingly enough - I emailed the tech editor at mopar action magazine, who told me that I had massive blowby and needed to buy a new motor. Is there any validity to this? Somehow I think a rebuild would be easier than completely swapping the engine (new ECM, if I buy another engine it's going to be something newer, so not OBDI compatible). His advice has always been sound for anything major, but somehow I just can't see a blowby issue as being cause for a new motor.

Mateo94XJ said:

Well, here's the plan - just got off work, headin' over to the shop.

I acquired a new rear main seal and oil pan gasket - so I'm going to start with the rear main, tighten the valve cover (as I recall it was hell to try to get those back bolts tight without a really long extension, maybe I need to try again) and check the sender.

Will report in later, see if my baby runs better.

Interestingly enough - I emailed the tech editor at mopar action magazine, who told me that I had massive blowby and needed to buy a new motor. Is there any validity to this? Somehow I think a rebuild would be easier than completely swapping the engine (new ECM, if I buy another engine it's going to be something newer, so not OBDI compatible). His advice has always been sound for anything major, but somehow I just can't see a blowby issue as being cause for a new motor.

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Where did he come up with blow by?
Is your air box full of oil?

Heh. This was an existing problem I had - I had to perform the MadXJ fix on the CCV setup. The hose would come loose from my air intake (I'm running Rusty's setup FYI) and shoot oil all over the intake side of the engine. I did this to alleviate that problem, and it works great. I went through a valve cover gasket, CCV hoses, and now what I believe is the rear main, which to its credit has leaked for a while, very minorly (a couple drops overnight for instance)

He asked if I removed the oil fill cap if smoke would come out, and it does. Hence my engine's going to blow up - the reason my main seal blew is because of blowby, which also blew all of my gaskets etc. I believe the quote was "Your rings are ancient history" and then he suggested an engine swap. When I said I didn't think it was nearly that bad, I was rewarded with the line "You can lead a horse to water. . ."

I think that idea may be applicable to 750hp smallblocks, but on a street Jeep motor, unmodified, it may be a bit of a stretch. I do have blowby - but it's not nearly as terrible as vehicles I've seen running just fine. Eventually it's something I'd like to fix. But as a college student, I'm fine burning a bit of oil, as long as the oil stays in the crankcase.

Also, I'm not going to be able to do this tonight. Looks like tomorrow afternoon it is.

I have a rule. Never replace anything unless you can prove it is bad first. Especially things that take a lot of work, like rear main seals.

Get a squirt bottle of Castrol SuperClean and spray down the engine everywhere there is oil. Wait a few minutes and rinse the engine. Repeat a couple of times until the oil is all gone. A quarter wash works great, just don't get the TPS wet too much. Then clean out the spray bottle and mix up some water and add a couple of tablespoons of cornstarch. Shake it up and mist the engine, especially where you had oil leaks. Let it dry. It will leave a white powder residue. If it is leaking just sitting, the leak will become readily apparent in a short time. The white powder will soak up the new oil and you will be able to track it back to the source.

old_man said:

I have a rule. Never replace anything unless you can prove it is bad first. Especially things that take a lot of work, like rear main seals.

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Good God that's brilliant.

I'll check it out, great idea. Give me something to do until I can haul it into the mini-baja shop tomorrow.

Mateo, pull the connector off the oil pressure sender and look for oil. I'll bet that's where your's is coming from. This is a high pressure fitting, and you can lose a lot of oil quickly, with just a small leak in the sender.

The clue is your having oil on the top of the oil filter.......

Runnin'OnEmpty said:

Mateo, pull the connector off the oil pressure sender and look for oil. I'll bet that's where your's is coming from. This is a high pressure fitting, and you can lose a lot of oil quickly, with just a small leak in the sender.

The clue is your having oil on the top of the oil filter.......

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Okay, it's dark now. I'll look in the morning.

It was a minor amount. . . but I'll check that, see if I can't fix that and return my rear main / oil pan gasket for another day.

Post in the morning with results.

Hey Runnin' On Empty!

I think you were right. If I'm not mistaken, there should be NO oil on the one plug that comes out of the oil pressure sender, right? I pulled mine and hit it with a flashlight, and sho nuff there was some oil on it. You mighta stopped me from barkin' up the wrong tree, say thankya.

I'l verify in the morning, and then return my rear main seal stuff, and then get me a new sender.

If you think I'm on the right track, well, two things:
1) Let me know!
2) If we ever go wheelin' together, you got a prime six pack of your choice comin' to ya.

Mateo, you've confirmed that the sender is indeed the cause of the leak. The inside of the plug should be completely dry. The sender seems to be leak-prone on the later models for some reason. My 96's is also leaking, and I plan to replace it this weekend.

The good thing about this fix is that it's extremely cheap and easy. A new sender is about $21 (verify it's for the correct indicator, either pressure warning light or gauge), and it takes about 5 minutes to install. That's not nearly as much fun as replacing a rear main seal.....

Good luck with it,
ROE

Runnin'OnEmpty said:

........ and you can lose a lot of oil quickly, with just a small leak in the sender.

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x2

I lost 11 quarts of oil in a 3-hour driving from a leaky sender.

_Maz