Mike, use a Helicoil Time-Set instead of an ordinary Helicoil.  The Time-Sert is a solid insert and will give better results if installed correctly.  The surface for the OEM drain plug will be restored with the Time-Sert thereby allowing the use of the OEM drain plug and a copper crush gasket.

Frank

> On Apr 13, 2018, at 11:00 PM, Automatic digest processor <LISTSERV@GERRY.VANAGON.COM> wrote:
> 
> Hello,
> 
> Some history first.  I owned my '84 since new.  About 20 years ago, the
> oil drain plug threads in the case stripped.  I inserted a Heli-Coil.
> From that point on, I cut a new cardboard drain plug gasket to use for
> each oil change.  One reason that I switched to cardboard was so I
> didn't have to tighten the plug very tight.  I never had a leak, until
> now.
> 
> Starting with the last oil change there was a small leak.  As time went
> on it got worse, but I thought that it would fix with the next
> cardboard gasket.  It didn't.
> 
> Because the shoulder on the OEM drain plug is small, I changed to an
> aftermarket drain plug with a wider shoulder.  It came with a nylon
> gasket which I then used.  It still leaked.
> 
> Today, I tried a cardboard gasket with the new plug.  It still leaked.
> 
> So, I took some photos.  They can be found at:
> 
>   http://5by9.net/busleak <http://5by9.net/busleak>
> 
> In photo a13.png, starting from the center, the Heli-Coil can be seen.
> Around that there appears to be an insert in the case, perhaps steel.
> Then, the case material can be see around the insert, as well as flaking
> plating of some sort.
> 
> What concerns me is the artifact at about 11:00 o'clock.  Both the
> insert and the case seem to be breached at this point.  Also, please
> notice the bubble in the plating above and to the left of the breach.
> 
> Photo a14.png is from a different angle and perhaps shows the artifact
> a little better.
> 
> Could oil be leaking through this breach, under the plating, and then
> out?  If not, what else could the leak be?  It's getting worse and will
> have to be dealt with.
> 
> Most importantly, what is the fix?
> 
> Thanks,
> Mike