I really like 3M professional products for this:
http://www.restockit.com/3m-trade-fast-n-firm-trade-seam-sealer-1-10-gallon-
cartridge-(mmm8505).html  You get what you pay for.

Stuart

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Liberte, Joel
Sent: Tuesday, November 20, 2012 10:42 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: '90 syncro with seam rust

Thanks all for the responses, while I'm lucky I don't have the kitchen to
deal with I have pulled the panels and indeedy there is rust on the inside
seams, had the same experience as someone recently filmed with water coming
through when raining.

Certainly no disagreement about making sure the entire joint is rust free
before doing anything, whether welding or body putty and believe I've made
my choice and agree with the majority; body putty.  That way if it isn't
cleaned out completely it's a heck of a lot easier to get back into later.

Lead?  Think I'd prefer the welding in that case.

Joel

-----Original Message-----
From: Stuart MacMillan [mailto:stuartmacm@gmail.com]
Sent: Tuesday, November 20, 2012 1:21 PM
To: Liberte, Joel; vanagon@GERRY.VANAGON.COM
Subject: RE: '90 syncro with seam rust

As others have said, this rust is also on the inside between the spot welded
flanges.  Covering this up with anything, including weldment, leaves the
problem to continue on the inside.  Cleaning and rust killing if the metal
hasn't rusted though can buy time, but the only permanent fix is panel
replacement.  Then you can fill the seams lightly with flexible professional
grade body putty, which leaves the seam sealed but visible.   Polyester
filler will crack.

I don't like the idea of welding.  The seams are part of the character and
originality of an '80s van, and cleaning up the bead would be a lot of work,
possibly more than panel replacement.

I feel your pain. I've been through this with my MGBs many times, but they
have far fewer seams, and they are leaded. (Yes, I've done leading, and it's
really not that hard.)

Stuart