Major leak issue with new engine install, need any and all help guys

[INSIDIOUS '86]

Keep an extinguisher on hand. A big one. Would hate for you to start it up and any fuel lighting up. All your fuel lines and rubber down the frame rails in good shape?
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[88Jimmy4x4]

hopefully it was old stuff, keep in mind the rear main sometimes wont leak real bad until it revs high, like driving around. Take your tq converter dust shield off and take a look underneath while its cold, then look after you run it

[UATahoe]

Thanks for the additional info guys. Really hoping it was just old stuff hanging around somewhere. After looking at the liquid that was coming out, i would say it is probably 90% gas. I dont think it would be possible for that much gas to be leaking out of the rear main. Thats the really strange part. I replaced all of the fuel lines with stainless braided hose from the throttle body to the fuel filter. Checked all the fittings and not a drop of fuel coming out. Dry as can be. I am going to roll it back into the driveway and see if anything else comes out. The fluid was running out like a faucet too. It was a slow leak by any means. If it would have been mostly oil i would suspect something different but if this much gas was in my oil i am thinking the engine would have had a catastrophic failure already. Thoughts?

[68Timber]

I know you're cringing at the rear main being the culprit but what everyone is saying does make sense.

[UATahoe]

Actually my concern wouldnt be with the rear main if that is indeed the culprit. Sucks to have to fix on a brand new motor but my bigger concern would be why and how did 3/4 of quart of gasoline leak out of it. LOL. That couldnt be good in any way. I am going to jack it up this afternoon to see if anymore fluid runs off. Dont really want to fire it up again until i am able to drain the oil and refill.

[UATahoe]

Jacked the truck up this evening. No more fluid, runoff or anything. When it leaked originally it was strong at first and by the time we were pushing it back in it had almost stopped. Tried to look up inside but not much you can really see actually. Going to change out the oil this weekend, fresh filter and then give it a test drive. I could see the rear main and it was as clean as it could be. At least the underside was. Bright clean alloy.
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[88Jimmy4x4]

Originally Posted by UATahoe

Jacked the truck up this evening. No more fluid, runoff or anything. When it leaked originally it was strong at first and by the time we were pushing it back in it had almost stopped. Tried to look up inside but not much you can really see actually. Going to change out the oil this weekend, fresh filter and then give it a test drive. I could see the rear main and it was as clean as it could be. At least the underside was. Bright clean alloy.
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excellent

[UATahoe]

Man I am taking it as a good sign and crossing my fingers. If the rear seal was leaking that bad, logic would say that alloy housing would be filthy. At least in my head I think that. Lol
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[mgchevyparts]

Sounds good, you may have had a large puddle of fuel that spilled over.

[UATahoe]

Well, bad news of course. Leak is back. Cranked the truck up let it run for about 5 minutes or so. Turned it off. Once it was off oil started leaking like a faucet. I dont believe its the rear seal though. I think it may be the oil pan gasket??? Once I got it on level ground, leak stops completely. Really bummed out over this whole thing. Not a good experience at all.
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[UATahoe]

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[UATahoe]

What do you guys think? Looks like a leak from the oil pan gasket to me.
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[mgchevyparts]

I'm trying to figure out this picture thing you posted.

[UATahoe]

Lol sorry. Looking up in between the Flexplate and the motor. You can see the stream of oil coming from the oil pan. It's leaking where the oil pan seals around the rear main seal housing
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[Sodell]

You may also have a fuel leak some where and it was leaking while you were running. First thing-drain oil from pan and see if it's the same consistency as the stuff in the jar. If you are looking at the dipstick it can be a little deceptive.

Just saw the prior pic post, that would make sense, the oil pan leaking on an incline. Did you put the oil pan on or the builder?

[UATahoe]

Builder installed. Fluid from the oil drain matched the leaking fluid exactly. It's definitely the oil pan gasket leaking. Guess it will need to be replaced. Better that than the rear main seal though. It still smells like gasoline. Without an exhaust system and without an o2 sensor, could that cause the gas in the oil problem? I am thinking it is just trying to pump in way too much gas since there is an absence of the o2 sensor.
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[Sodell]

That plain sucks!!

You were trying to get it started for a while. I would not worry about the smell too much, but I would keep an eye on it.

[LynnJr]

I would buy a fresh roll of paper towels and some starter fluid.Starter fluid works better than carb cleaner were I live(california) for cleaning oil.
Get that engine spick and span clean and dry.
Now start it up for 15 seconds shut it off and get under it quickly with a fresh paper towel in hand.
All your oil leaks will run to the rear of the oil pan because the motor sits on an angle so work your way up constantly looking for any oil on the paper towel.
If the front of a valve cover leaks it will run down the bottom edge of the cover then run down the back of the pan.
I tend to find most leaks at the rear of the engine around the manifold.I pull all the plugs and after getting everything spotless and dry I crawl under the truck and have a friend spin the motor over until I get oil.
Your pan is probably full of gasoline right now so make sure it isn't forcing oil out of the dipstick when its running.

[UATahoe]

Small update here. Got the exhaust installed today. Towed it to and from the shop. O2 sensor is now installed so hopefully it will run much better. Not going to have a lot of time this weekend but planning on dropping the oil pan on Monday to check out what's causing the oil pan leak. Get fresh oil and a fresh filter in there. Look over all the vacuum lines and then go from there. Gotta trouble shoot my electric fan relay too. The thermostatic switch that is supposed to kick them on isn't working. If I jump the 2 wires they come right on so I have narrowed it down to the switch. May need a new one. Not sure. Slowly but surely I will get this thing squared away. Lol. Starter is a bit noisy too so I need to do a little adjusting on it as well. Break out the timing light to make sure the timing is squared away. A lot of little things but hopefully I can attack most of them Monday.
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[nheller76]

I am reading this hoping that i will not have this problem with my new motor! I am soooo sorry man! Chasing leaks feels like your pulling your nose hairs out one buy one!

[68Timber]

You'll get it figured out. I'm waiting to hear how a TBI stroker motor runs.

[UATahoe]

I really do feel like I have a good handle on how to fix all the small issues. Getting to hear it fire up today with the new exhaust definitely made me smile. Lol I am definitely ready to take it for the first drive. More anxious than anything and patience has never been a virtue of mine. Lol
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[UATahoe]

Got a big update. Finally got the oil pan dropped and replaced the oil pan gasket. Put 30 miles on the truck this afternoon. Hasn't leaked a drop!!!!!!! Man did it run great! And the gas/tach combo is working perfectly! I am so stoked! Dropped it off at the tranny shop to get the tv cable adjusted properly. After that, just gotta figure out why the thermostatic switch isn't kicking the fans on. Just jumping them now to make sure it doesn't overheat.

But it definitely feels good to have a running truck again!
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[Sodell]

Awesome news, glad it wasn't anything more than the pan...

[Rufton]

Congrats!
Don't let that heat sneak up and bite the heads