Just checked mine before coming in the house.  question had me curious.
you are correct.. the cap on the 82 westy is vented.   to get to that
cap you have to open the cabinet and remove the metal "floor" to expose
the water jug cap.
jimt
On Wednesday, September 11, 2002, at 06:48 PM, G. Matthew Bulley wrote:
> Replace faucet. RV dealer.
> No "vent" per se. The little panel under the rearmost luggage, bin
> conceals a pin-hole in the clean-out lid.