David Beierl wrote:
>
> They blow off.  They are meant to keep out water when you're washing the
> van, or for winter storage to keep wasps out.  Not meant for driving
> with.  The camper manuals says "put this on when washing the van."

I'm new to the list ("Hello all") and proud new owner of an '85 Westy
with 57K original miles. The area behind the driver's door below the
fill tubes, etc. is very rusty along the seam between the upper and
lower side panels. I first thought this might be caused by overflow from
either using public water or filling the water tank. From this post, I'm
curious as to whether the rust might have originated from water entering
the vent (without a cap -- as I didn't know such a device existed). I
plan to remove the rust as best I can but I would first like to
determine its cause.

John Fried
'85 Westy