Forgot to post this here, seems the new replaceable valve core tubes Surly has for fatbikes will leak air. I got one recently that did this. I fixed it by wrapping a small piece of plumber's tape around the valve core threads. Even with the tape on, it seemed to screw back in rather easy. Saw the post in the bike shop news forum where someone had the valve pop out when removing the cap. Not surprised, I've seen this happen with other replaceable valve cores, but usually just means tightening them down and check them from time to time. With the fatty, I did that but it still leaked until I taped it.
It's been good since the Farmer's race, never leaked once.