Sure looks like residue around there.  Have you pressed hard on it to watch
for it to open up or leak a little, maybe when it is hot and pressurized?
  You should also be suspicious of the seal (O-ring?) around the level
sensor.  If you pull the sensor out you can also see whether the "crack"
extends into the threaded area.

Larry A.

On Wed, Apr 29, 2015 at 11:01 PM, Neil N <musomuso@gmail.com> wrote:

> I'm a lucky duck?  (I think I found the issue)
>
> image of coolant expansion bottle: http://tinyurl.com/lanaowm
> Does this look like a crack?  Image:  http://tinyurl.com/mx7ujr5
> Sorry for pic quality. These were taken with my phone camera.
> As per Jim's magnifying glass comment, I only noticed what may be a crack
> when I viewed the image on my laptop.
>
> If the leak were slow enough, maybe coolant evaporates off the bottle
> before hitting the ground? It looks like there's residue due to
> evaporation process.
> Anyhow....
>
> I hope this is the cause!
>
> Neil.
>
>
>
>
>
> --
> Neil n
>
> Blog: Vanagons, Westfalia, general <http://tubaneil.blogspot.ca>
>
> 1988 Westy Images <https://picasaweb.google.com/musomuso/New1988Westy>
>
> 1981 Westfalia "Jaco" Images, technical <http://tubaneil.googlepages.com/>
>
> Vanagon-Bus VAG Gas Engine Swap Group <http://tinyurl.com/khalbay>
>