36HP Oil Leak

[johnbrad]

Have just started up our rebuilt engine (aircraft conversion based on 36HP) and have an oil leak form the middle bottom crackcase through-bolt. No oil weeps when static, then a small oil dribble only when the engine is running. Is this a common problem and what is the best cure? Does this mean we have a potential problem with the main bearing joining faces leaking oil? Also, the oil presure was less than I had hoped for a rebuilt engine, 40psi, I was expecting somewhere near the relief valve setting of 60psi when cold.
Any suggestions or help would be appreciated.

[spectre6000]

I think 40 psi is about what you want. At 45 psi the oil cooler closes off so the cold thick oil will warm up.
_________________
Jason Hopper

-'58 German Market Deluxe Beetle (in progress)
-'84 M1009 CUCV
-'81 K10
"Buy the best, cry once." -Gene Berg
"A cheap man will always buy the cheapest thing available, and then buys another one hoping for a better result, and then spends the rest of his life in misery complaining about it. A thrifty man will buy a good part once and never think about it again." -RockCrusher
"Don't feed the Shitty Parts Monster!" -Me

[Motorhead55]

It is a general practice to use some kind of sealant on the case half washers where they meet the case. Back it off all the way, if you can get to it, clean the area and washer, reseal it and run the engine.I think about 1970, VW started using self sealing case half nuts and no washer. Less torque required with the self seal nut.
An old German wives tale..... "No one ever worried about a VWs oil pressure until they put a gauge on it!"
40 PSI is good. You can put a early 1500, 6mm stud hole oil pump in it for more volume and maybe a little more pressure.
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2007 Dodge Cummins Diesel 4x4 6spd stick
1939 WILLYS pickup
1967 Triumph Tiger Cub

[Snort]

I can't imagine starting an aircraft motor rebuild with any suspicious oil leak. A case main bearing stud under normal automobile conditions should only weep at worst, not dribble. I think you should take it apart and examine the case for cracks and other wear, spot face the right side of the case where the nuts and washers fit, and try again with some quality sealant under the washers.

Perhaps you are referring to one of the outer case bolts? Even if one of those are leaking, I would think that even though it wouldn't be connected to any oil pressure area, you still need to open it up and get it sealed properly. It could be cracked as well, and leaks more when the engine warms up.

[johnbrad]

Many thanks for the replies. I feel much happier about the oil pressure.
I am more concerned about the why the oil is able to get up the stud hole
under enough pressure to come out through the stud/nut threads. The oil only dribbles out with the engine running and stops when the engine is stopped. The cases were replacement items, which after crack testing and measurement were approved as serviceable. It's as if the main bearing web faces are not quite coming together and allowing oil under pressure to get from the oil gallery in the centre main bearing web across the face into the stud hole. Is this a known or common problem? Our old cases were distorted and the main bearing webs badly fretted causing the original low oil pressure problem.

[johnbrad]

Problem solved, I should have looked a bit closer at the original crankcase!
The middle thro-bolt hole is connected to the oil gallery on the LHS crankcase, hence there is oil pressure round the bolt. All I have to do is keep the oil inside with sealing washers and a domed or new self-locking nut. Thanks for all the comments.

[paf]

Hello,

I may have the same problem on my 36hp installed in my beetle. I was suspecting the cylinder 1 to be the cause of the oil leak, but while dismantling it, it seems that is is more related to these 3 bottom crank case bolts, especially the middle one. I am wandering if you did what you intended to do to your engine, and if the result is conclusive. I intend to do the same : unscrewing one by one the bottom bolts, clean them, apply sealant and screw it back at the correct torque.
_________________
Fred
Euro '58 L334 bug
http://www.thesamba.com/vw/forum/viewtopic.php?t=657333

[paf]

"johnbrad" last visit in 2011, I will not have any answer, I think... pity. I confirmed the middle nut is leaking. I will do the same thing. By the way anyone can say if using M10 self sealing dome nut is feasible in lieu of current washer-nut-sealing compound ?
_________________
Fred
Euro '58 L334 bug
http://www.thesamba.com/vw/forum/viewtopic.php?t=657333