An Odd oil leak

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Dongshoreman
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An Odd oil leak

Postby Dongshoreman » Sun May 14, 2017 9:24 pm

Hey guys,
I finished up a bunch of work on my '83, and I'm finally up and running! After the second test drive I was looking underneath for any signs of leaks and I found small amount of oil leaking from the heads of the two M6 bolts that are in the rear corners of the crankcase that hold the case together. Here are some pics of the bolt (sorry about the pic quality it was hard to get light under there and snap the pic at the same time):
20170511_115856.jpg
20170511_120324.jpg


The bolts are not oily in these pictures because I had just wiped them clean.

Though it is not a lot of oil coming out, I would still like to stop the leak. Any thoughts? I was thinking I could just loosen those bolts, plug the holes with some RTV and then snug them back up, but I thought I'd throw it out there in case anyone else has ever seen this before.

Thanks,
Jake
1983 Diesel Shortbed

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JoeIsuzu
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Re: An Odd oil leak

Postby JoeIsuzu » Sun May 14, 2017 9:41 pm

Wow, I was about to post a similar question, with similar pics. I haven't even checked the driver's side, but mine seems to be leaking from the same vicinity as yours. I'm losing a quart of oil in about 150 miles. So I'll wait, and maybe we'll both get answers.

Jack

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Re: An Odd oil leak

Postby woodbutcher55 » Mon May 15, 2017 7:52 pm

I had a similar leak on a 81 that I never got fixed, but the best I could tell the rear main seal was the culprit. But I'm not 100 % sure ,but if you reseal those 2 bolts and it stops leaking your lucky. Anybody?

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Dongshoreman
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Re: An Odd oil leak

Postby Dongshoreman » Mon May 15, 2017 8:17 pm

I just got finished replacing the rear main seal, oil pan gasket, sending unit, oil hose from the case to the pan (the brown house in the picture above), oil cooler o-rings, and the oil hoses that go to the vacuum pump. Those all seem to be holding oil ok, but it seems the oil is weeping from those bolts.
1983 Diesel Shortbed

woodbutcher55
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Re: An Odd oil leak

Postby woodbutcher55 » Mon May 15, 2017 8:37 pm

I replaced all of those too but my rear main started leaking again. Either I didn't put the main seal in correctly or the old seal wore a grove in the crankshaft causing the new seal to leak. This is just a guess.

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Re: An Odd oil leak

Postby downunderyank » Tue May 16, 2017 11:52 pm

Yes, I've seen where the old seal wore a groove in the crank. I've used speedy sleeves to fix this or if you can position the new seal further inboard or outboard so it runs in a different spot on the crank.
converted '86 diesel spacecab

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Paul
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Re: An Odd oil leak

Postby Paul » Thu May 18, 2017 7:00 pm

Hey you guys - -

I just took a look at an engine that has the pan off and it appears that those two bolts are two of the many that hold the center aluminum section of the crankcase to the cast iron block. No other purpose.

I remember that when I overhauled an engine a year ago that that aluminum section is supposed to be sealed to the block (and all around every bolt) with something like the 'Right Stuff' or black RTV. There is no gasket used at this joint.

I think that your engines were not sealed around those bolts so good, letting the oil seep around the bolt and down to the head.

I think that if you remove the bolt and clean it and the hole real good and then use a lot of 'Right Stuff" or RTV around the bolt and into the hole it will seal up OK and not leak. No worries. :D :D

Paul
'84 P'UP 2 wd diesel, 5 spd with 0.78 fifth gear and differential back to 3.73.

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Dongshoreman
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Re: An Odd oil leak

Postby Dongshoreman » Fri May 19, 2017 11:30 am

Awesome, thanks for the reply Paul. I'll give that a try and see if the leaking subsides.
1983 Diesel Shortbed

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puttputtinpup
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Re: An Odd oil leak

Postby puttputtinpup » Fri May 19, 2017 3:23 pm

If that doesn't work, try some plumbers thread sealer with Teflon. Like Teflon tape but in a squeeze tube
Currently P'up-less, but keeping my eyes open for a good deal
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Odd Oil Leak Updates

Postby Dongshoreman » Sat Jun 17, 2017 11:03 pm

Hey guys,
Here is an update from the earlier "Odd oil leak" post. I loosened the bolts that hold the crankcase together, cleaned them really well, and then I coated the base of the heads in red RTV silicone. After running the truck a couple times I took a look at the bolts and they look clean, no noticeable oil leaking from them. Here are two pics:
20170615_192117.jpg
20170615_192257.jpg


For the two rear bolts I could not completely remove them because the oil pan is in the way, so I just loosened them and let them rest on the pan while I cleaned them. I completely removed the two front bolts and put some brake cleaner on a Q-tip and cleaned the hole really well so the RTV would stick. It looks like it's holding the oil nicely so I'm in good shape. As you can see from the top picture I still have some oil leaking down the front of the pan, and I suspect it is coming from the front seal or the camshaft seal. The adventure continues...
1983 Diesel Shortbed

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JoeIsuzu
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Re: An Odd oil leak

Postby JoeIsuzu » Sat Jun 17, 2017 11:17 pm

I merged this into the original topic. It helps to have that backstory. Glad this seems to have fixed it. Please update here if anything changes.

Jack

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Dongshoreman
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Re: An Odd oil leak

Postby Dongshoreman » Sun Jun 18, 2017 7:51 am

Will do. Thanks Jack.
1983 Diesel Shortbed


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