[overlander64]

Greetings Leigh!

If you can see a crack on your sink that is likely the problem, but if you can't; I believe that it may be a less involved repair. At the ages our coaches are getting to be, my thought is that the plumbers putty that seals around the drain flange may have dried out and failed creating a path for water - - espeically when water is held in the sink by plugging the drain. The fix is relatively easy - - removing the drain assembly (held by rather large fittings that often respond best to a moderately large adjustable wrench), then clean any old plumbers putty from both the sink surface and the fitting - - then take the fitting to a plumbing store and obtain replacement gaskets as necessary as well as some fresh plumbers putty. Reinstall the fitting with putty where it rests in the sink - - tighten very carefully just until a uniform bead of plumbers putty is pushed out around the fitting. (If you haven't guessed, I had this problem earlier this Spring.)

I can't guess what the second vent is unless it would be for the range exhaust (but it is a flat metal fitting on my coach and more on the side). I too believe that one of the vents would likely be for the refrigerator.

Good luck with solving your repair issues!

Kevin