The coolant reservoir behind the license plate has a rubber gasket on
the *inside* of the cap.  This keeps the coolant from draining out the
cap threads when things really heat up and the level is above the cap. 
The protrusion on the top of the tank has holes in it for venting, so no
worries there.

I left this cap a little loose once, not sure how, but was terribly
worried when I saw some coolant on the ground last summer.  Tightened
the cap and all is well.

Gregory Smith
Smith Design Studio
Small Building Company
Olympia, WA
360-239-0429
gregoryfsmith.com