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Oil leak below head gasket level

malohnes

Well-Known Member
Joined
August 8, 2009
Messages
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City, State
SE Alaska
Year, Model & Trim Level
'91 xl m5 4x4
I've got a oil leak that I can't put the kabash on. It's driven me nuts man and I need your help!! :scratch:

So, it isn't a typical drip leak. Though I do have one of those from a leaky rear main seal. It only seems to happen while driving more than town errands and coats the undercarriage of my truck from under the front main seal all the way back to the t-case, especially around the oil filter side, the starter side isn't too bad though. At idle I see nothing spraying or dripping, yet after a drive down the highway and back its all over the place. I detailed the engine bay in the fall for winter driving and degreased everything so it was pretty tidy and clean outside of the grime I didn't brush out.

Looking for stains and wetness, it's below the head gaskets. (though I have a light seep from one head's valve cover) Checked oil filter and it's fine. I have a oil filter cooler and the sandwich adapter was a little loose but snugging it down did nothing. I recently discovered that and after a 4 hour drive the leak wasn't noticeably better.

The leak really should be a spray of some sort because the area covered and the volume is not especially high, but is enough to make a mess and drip from the oil pan area, the tranny drain plug area and the oil filter, once it sits after a drive. It reminds me of the leak from the manual tranny when the shifter plugs leak, sloppy.

Can't think of anything else thats pertinent. What are some causes for a leak of this nature?

I'm missing something obvious, like looking for the peanut butter jar on the shelf right in front of my face!!! :mad:
 



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Oil pan gasket?
 






Have you ruled out the oil filter itself or the adapter?
 












Have you ruled out the oil filter itself or the adapter?

Yeah, filter for sure as its new as of 2 days ago when I discovered the adapter was loose

The adapter, not so sure yet but the weather has created a single Dow today fir me to crawl and play around today. Given it didn't leak like his after I installed and didn't. When it was loose I'm not inclined to feel it's the source but I still am suspicious.
 






Here's what my oil pan gasket failure looked like:
https://dl.dropboxusercontent.com/u...rer/Pictures/CameraZOOM-20140929102113950.jpg

After I cleaned it and ran the engine for a very short while (under a minute):
https://dl.dropboxusercontent.com/u...rer/Pictures/CameraZOOM-20140929103754336.jpg

Mine looks very similar but much worse! Mostly the grimy mess from not looking for several months since the fall. Does the pan have pressures? I understood not beyond crankcase pulses and the mess really seems to be pressure related.
 






I'll look for loose pan bolts, but if I do have a failure here, this will cramp my style big time. Though I have a fresh pan gasket, this isn't something I can replace in truck... Insert sad, mad face here

Any other sources I should look at?
 






There shouldn't be pressure in the crankcase or sump but the oil still leaks out. Clogged PCV wouldn't make a difference in our vehicles since the passenger side is still ventilated to the intake tube (normally air intake side when the PCV is working).

Loose bolts won't help you. The gasket shrinks up and becomes very brittle;
https://www.youtube.com/watch?v=7Pj_933njSg

At that point, you're sealing aluminum against cast iron and that doesn't work out too well. For your sake, I hope it's something else but this is a common item.
 






There shouldn't be pressure in the crankcase or sump but the oil still leaks out. Clogged PCV wouldn't make a difference in our vehicles since the passenger side is still ventilated to the intake tube (normally air intake side when the PCV is working).

Loose bolts won't help you. The gasket shrinks up and becomes very brittle;
https://www.youtube.com/watch?v=7Pj_933njSg

At that point, you're sealing aluminum against cast iron and that doesn't work out too well. For your sake, I hope it's something else but this is a common item.

Yeah, not liking the options. I'm gonna clean the whole area as best as I can and then pull the oil filter and the sandwich adapter again, check for loose fittings and see what happens. New engine mounts are on my list of projects and lifting engine is required for that, so may be if it comes to it I can kill two with one. Gotta read up not he threads related to pan gasket. I know its tricky around the main bearing areas.

I don't have a garage to work in so I'll be at the mercy of the weather and the elements to make this happen. I might be able to convince a buddy, but everyone is wrenching on projects right now that has a lift and garage.
 






Its not conclusive, but I think it really is as simple as the pan gasket.

The filter and sandwich assembly are fine. The o-rings are in good shape and are intact. The rubber lines to the oil cooler are not leaking either.

After searching some threads, i came across two using SOHC pans and the flat metal gasket that goes with it as interchangeable with OHV blocks, BUT, you have to use the SOHC pan and flat gasket or the OHV pan and the corresponding gasket. can't mix them and expect a seal.

On an other thread, a fella lifted the engine up, but not out and said he was able to pull the whole pan out and reinstall the pan after cleaning the block, but did not remove the engine. He appeared to have pulled the tranny and t-case. Another thread mentioned that loosening the tranny mount and engine mounts and jacking up the engine from the tranny yielded enough space to change the pan gasket without much trouble.

As i see it, the only way to do the job without lifting the engine/tranny out or removing the tranny and t-case is to drop the front end. The TTB beams are in the way.

So, my thought it this. Im looking to regear my axles. If I remove the pumpkin, to do that job, pulling the beams out isn't too bad. Then I can access the pan and clean the surfaces and be done with this messy business. Jacking the engine up may still be done so I can replace motor mounts, but it should ease the pan issue and to me, pulling the front end is easier than pulling a motor. Ive pulled the front end before and its straight forward.

Thoughts?
 






I think I have an oil pan gasket that needs replaced as well. I still need to get under it and clean everything up real well but I'm afraid that's what it is.
From what I've found it you're really good and patient you can jack up the engine after loosening the engine and trans mounts, drop the pan and have enough room to get the old gasket out and fish the new one over and under everything since you're basically working with a giant rubber band. It sounds like it should be easy if not tedious, but still scares me enough that I haven't tried it.
This summer I think I will...
 






I think I have an oil pan gasket that needs replaced as well. I still need to get under it and clean everything up real well but I'm afraid that's what it is.
From what I've found it you're really good and patient you can jack up the engine after loosening the engine and trans mounts, drop the pan and have enough room to get the old gasket out and fish the new one over and under everything since you're basically working with a giant rubber band. It sounds like it should be easy if not tedious, but still scares me enough that I haven't tried it.
This summer I think I will...


There is a reason most owners just live with the leak until rebuild time. Its a very doable job, just a major pain in the tail...

The trouble with this method is you can't clean the block or the pan surfaces. Failure to do that means a high likely hood of failure.

In my case, with the pumpkin removed, i'll have much out anyway, so pulling the rest out of the way isn't so much work. Still mulling it over...
 






So what you're saying is if I was smart I would find a wrecked Ex, rebuild the engine and swap them instead of playing with this. That's what I should do then I don't have to worry about any of it.
This is ultimately what I want to do anyway.
 






The surfaces don't have to be super cleaned since it's not a typical gasket. It's basically an o-ring that puts pressure on both surfaces.

One thing to note, at least on my 1991 but I'd imagine it's the same for others, the transmission bolts into the oil pan. I don't think you could use an SOHC pan unless the tranny bolt pattern happens to line up.

I'll be totally honest here... I pulled the engine for mine and did the rear main seal at the same time. Mine still leaks. I don't know if I botched the rear main seal job (used an SKF with one of those sleeves) or if my idea to add RTV on the outside of the oil pan gasket bead was a bad. It doesn't leak anywhere near as bad as it used to but the underside is wet and I'll occasionally leave a drop. More importantly to note, my tranny leaks more now. I think in the process of fighting the engine re-installation, the pump seal might have gotten damaged slightly. We didn't ram it back together but it was a bit frustrating. It doesn't puke out transmission fluid but it'll leave a drip or two in addition to what the manual gear input shaft leaks.

It's a tough call when you split the engine & trans. Do you replace the rear main and input/pump seal or just leave it as-is and hope it lasts? Maybe you replace it and it's fine. Maybe you jar it while re-installing and it leaks. Kind of a gamble in my opinion.

I'm glad I pulled the engine for mine, I was able to do other work at the same time. I sure couldn't have gone with it leaking as it was, a quart and a half every 400 miles. But... it wasn't easy either.

malohnes, I think you have it right to do it with the axles removed when you do pumpkin work. No splitting of the engine & trans there and you'll have a fair amount of room to work. Since you have a manual, you won't have cooler lines in the way.
 






Dumb question but if it was my oil pan gasket, shouldn't I leave a puddle where I park? That's the one thing I've never understood. For the amount of oil I go through, it seems like I should see it where I park, or put up a smoke screen when I drive, neither of which I do.
 






Dumb question but if it was my oil pan gasket, shouldn't I leave a puddle where I park? That's the one thing I've never understood. For the amount of oil I go through, it seems like I should see it where I park, or put up a smoke screen when I drive, neither of which I do.

Kirby, I have a small drip, no pooling. That is part of the reason why i was stumped. It never occurred to my the pan gasket was the culprit cause I expected it only to be when under pressure. I actually get a film of oil on my back window after a 4 hour drive, which I do frequently.

I also just replaced my PVC valve and that actually made a difference in the amount of mess under the truck.

Sometimes these things aren't exactly as we expect and it is why I love this forum so much. So many experienced owners who usually know their stuff means the answer is never far and you're rarely the first to experience your issue.
 






Mine leaked for a couple weeks but it never soaked the underside of the car, it didn't even fully wet the transmission. Never anywhere near as far back as the rear window though.

Maybe our driving habits are different? I don't see a ton of highway miles.

Mine tended to make puddles, even after shutting off the car. That's what bugged me the most. I'd go somewhere and leave a softball-sized puddle of oil. Maybe since I don't travel on the highway much, it never blew off of my pan but rather collected and then dripped off when I parked?


SuperKirby, if you don't have any puddles when you park, even a couple drips, I'd lean towards oil rings or valve stem seals.
 






Rings are a possibility as I don't know for sure how many miles are on it. Could be the first or second or 18th trip around on the odometer. For the condition it's in I'd like to think it's 13x,x.. miles but I don't know. I replaced the heads when I got it as the head gasket was leaking and I had both extra money and no time to wait to have them resurfaced. The heads I bought were complete with new valves, seals, etc. I'd like to think it's not the case but again, who knows.
I'm still leaning towards the pan gasket as my biggest culprit and just in denial. The bottom of my engine is pretty coated in oil but doesn't leave a lot for drips. A few here in there but not a concerning amount. Not much for blue exhaust or what I would consider exhaust that looked concerning.
My last ditch hope is I think I need to redo my LIM gasket and was hoping that if I put better valve cover gaskets on it might help some. When I did the heads it came with cork gaskets. I had a bad feeling about putting them on but it was 2 am and I needed it the next day so used them. I doubt it's the sole source of problems but hey, it sounds better than the oil pan.
As it sits now I'll probably be attempting the oil pan gasket this summer
 






Also I apologize for hijacking this thread from the OP
 



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Rings are a possibility as I don't know for sure how many miles are on it. Could be the first or second or 18th trip around on the odometer. For the condition it's in I'd like to think it's 13x,x.. miles but I don't know. I replaced the heads when I got it as the head gasket was leaking and I had both extra money and no time to wait to have them resurfaced. The heads I bought were complete with new valves, seals, etc. I'd like to think it's not the case but again, who knows.
I'm still leaning towards the pan gasket as my biggest culprit and just in denial. The bottom of my engine is pretty coated in oil but doesn't leave a lot for drips. A few here in there but not a concerning amount. Not much for blue exhaust or what I would consider exhaust that looked concerning.
My last ditch hope is I think I need to redo my LIM gasket and was hoping that if I put better valve cover gaskets on it might help some. When I did the heads it came with cork gaskets. I had a bad feeling about putting them on but it was 2 am and I needed it the next day so used them. I doubt it's the sole source of problems but hey, it sounds better than the oil pan.
As it sits now I'll probably be attempting the oil pan gasket this summer

If I were you, I'd redo your LIM and valve cover gaskets first. They're easy to do and, if, it cures your issue then great. Also replace your PCV valve.

My gut tells me you're on the same boat as me. If you don't have blue smoke, I wouldn't lean on the ring concern too much and attack an easier solution than full rebuild. Its not a hard project, just a lot of work. I'm convinced it doesn't require splitting the engine and tranny.
But I'm also in a unique position of dropping my front end to access the pan without messing with the engine from above. You might entertain that option as well. Last year I replaced the whole front end, so mine should come apart quickly and relatively easily.

Don't sweat hijacking the thread, we're both basically in the same boat.
 






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