Hmmm.... I've dropped and reinstalled Vanagon tanks probably 4 times.  I've
never had to use lubricant to install the fill pipe in the donut, and I've
never had a leak there, either.

Are you sure it's the fill pipe/tank junction is leaking?

If so, I'd drop the tank once again, get a new gasket (though, I *have* used
old ones successfully) and try reinstalling.  Somehow I don't think it's the
WD-40 per se, though I think the lubricant typically recommended is some
Vaseline.

Here's the write-up I prepared for dropping and reinstalling the gas tank

http://www.type2.com/archive/type2/107822.html

if that's any help.
---------------------------------------------------------------
Tom Young                       '81 Vanagon
Lafayette, CA 94549         '82 Westfalia
---------------------------------------------------------------
----- Original Message -----
From: "Michael S. Nichols" <msnichols@MINDSPRING.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, September 05, 2004 3:19 PM
Subject: Leaking Gas tank donut gasket!

> Today I dropped my '81 air cooled gas tank and
> replaced the old fuel lines and the large donut gasket for the tank fill
> pipe.  I have been unable to wiggle and reset the fill pipe in such a way
to
> not leak gas when the tank has 12 gal+ in it.  I tried to push the pipe in
> the donut gasket without any lubricant, and it would not go.  I then put
> some WD40 on both the pipe and donut gasket, and they went together
> easily----too easily, perhaps?  Short of taking my Van into a service
center
> to fix this, does anyone have any ideas as to what I did wrong, and what I
> can do to remedy the leaking gas problem?  Should I remove the fill pipe,
> clean off the WD 40 from both the gasket and the pipe, and use something
> else, or use no lubricant?