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Main seal oil drain hole in case - why at 7 o'clock?
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Ted in Tallahassee
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PostPosted: Wed Jan 22, 2014 4:29 am    Post subject: Main seal oil drain hole in case - why at 7 o'clock? Reply with quote

I'm in the middle of rebuilding my '73 Thing engine and wondered why the oil drain hole in the area at the front of the case where the crank & main seal go has a factory drilled oil drain hole at 7 o'clock, and why many VW mechanics often drill another one closer to 6 o'clock to prevent oil from pooling there and leaking. This was done to my case 17 years ago (last build) by my local long time VW mechanic while I had taken the case to get align bored. At the time he said he always does that (drill a 6 o'clock hole) because if you don't, "they always leak."

I got to thinking about this when I was in the process of setting my endplay. I did not fully understand why the tolerance range (.003" to .005") was so narrow and so critical to stay within and why 3 spacers (shims) and not 2 or 4, and in doing lots of research (mostly posts here), I understand it now--in short, you want JUST enough linear movement so as to allow each of the three spacers to have a film of oil on them so there are 6 surfaces covered with oil. Not enough endplay, not enough oil, and the spacers can gall, heat up, and bind, causing the crank to bind to the main #1 (thrust) bearing in the case, spinning it, and seizing he engine. Too much space allows the crank to slam against the thrust bearing too much, and over time it will beat it and beat it to the point it pounds out the saddle in the case.

So in consideration of all that, I am thinking the German engineers very purposely put that oil drain hole right there at 7 o'clock, so there would always be a pool of oil there just touching the bottoms of the shims, bathing them in oil, keeping them nice and wet. Drilling the second 6 o'clock hole allows the draining of that oil. Yes it will prevent leaks if your seal is faulty in some way (improperly installed, cracked, tilted, torn, scraped, case is gouged at the sealing surface), but the bottoms of the shims are not as wet as they were/are supposed to be, and now must rely on the little bit of oil that seeps from between the crank and bearing.

Looking at my spacers after being in there 17 years, they do look a little galled, and one has a perceptible concave or dished look. I have ordered new shims (of various sizes so I can set it right with three) and was wondering what you guys thought about this theory, and whether you think I should plug up that 6 o'clock hole before fully reassembling the engine so there will be that little puddle of oil sitting there bathing the bottom of the spacers.
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Multi69s
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PostPosted: Wed Jan 22, 2014 9:55 am    Post subject: Reply with quote

Post up some pictures of your case, so we can see what hole you are referring to.
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Mr.Duncan
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PostPosted: Wed Jan 22, 2014 10:51 am    Post subject: Re: Main seal oil drain hole in case - why at 7 o'clock? Reply with quote

Ted in Tallahassee wrote:

So in consideration of all that, I am thinking the German engineers very purposely put that oil drain hole right there at 7 o'clock, so there would always be a pool of oil there just touching the bottoms of the shims, bathing them in oil, keeping them nice and wet. Drilling the second 6 o'clock hole allows the draining of that oil.


Good idea, makes sense!

(if they did a 6 'oclock drilling it wouldn't work well due to that being between the case haves seem..)
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