Thanks (pdooley, Zoltan, Zoran & Scott).
Too late for me to add additional sealant, but the o-ring and the new t-stat are
installed.
That's a difficult place to work, for me, anyway and the forward left bolt on the
cover was especially challenging, with the big A/C hose running right over the top of
it. I did disconnect 3 coolant hoses so I could move things around.

FWIW, the old t-stat was for an Audi (PN078 121 113F). It has what looks like a
check-valve on the flange. Been in there for 9 years and over 50K miles, so I can't
say it hurt anything. Installed by a VW auth. repair shop in Prescott AZ.
Jerry

----- Original Message -----
From: "Scott Daniel - Turbovans" <scottdaniel@TURBOVANS.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, April 07, 2009 11:56 PM
Subject: Re: seal at lower t-stat housing to cyl head

> in any case, a round o-ring is right there,
> and .........installed it with a high quality silicone sealant., on the
> o-ring and the flange where it goes against the head.
> Any o-rings installed dry leak after a while in my experience.
>
> scott