No, this isn't a line balancing/kegging issue that's in the wrong forum. I wasn't sure where to put it so mods feel free to move it if you feel it should go somewhere else.
This is really weird. So last night I bottled up my IIPA, keged my Alt and did some cleanup. I was in the basement and realized that it had been probaly 60 days or so since the last time that I vented the kegs that I have my Old Ale and my Biere de Garde aging in. I put both beers in kegs after secondary for long term aging, with plans on force carbing them sometime next month. No pressure was put on either keg and no priming sugar was added.
So I vent the Old Ale keg - nothing. It's still, as it should be.
I vent the BdG keg and it sounds like it had 15 psi on it. I wait a couple minutes and pull it again and I get sprayed with foam. So I grab a towel to surround the sides of the pressure relief valve and I open it up to bleed out the foam. I finally get enough pressure out of the keg that I can get the lid off and the foaming doesn't stop. It's not gushing by any means, but it slowly continues. I sanitized a spoon and scooped some of it out, but it keeps coming.
I sanitized a turkey baster and pulled out a sample to see if I could taste an infection of some type, but the sample tastes the same as it did 6 months ago when I put it in the keg. There is a small amount of carbonation present in the beer, which would explain the pressure, but what really gets me is that this beer was at 1.003 when I kegged it and it had remained at 1.003 for 30 days prior to getting put into a keg for aging.
I'm confused as to what could possibly be causing the foaming, but I'm not overly concerned since the beer still tastes as it should.