I have a two T3s tanks, and gave my brother an MT3s. They've worked pretty well (though they pale in comparison to my new ProTank 2), but I had one start gurgling on me the other day after a fill. I tried dry burning, running a pipe cleaner through the stem and drip tip, to no avail. I unscrewed the tank and left it sitting upside-down on my desk, hoping this would cause it to drain out of any liquid that might be stuck in the stem somewhere. After a while I said enough was enough.
So I unscrewed the T3s off my battery I had put it on that day and noticed there was a layer of liquid between the T3s and the battery. Uh oh. I wiped it clean then unscrewed the base off the tank. I then unscrewed the coil head off the tank and this was when I noticed that it was on there extremely tight. Once it was off, I screwed it right back on, without putting it too tight, and presto! No more gurgling.
I think the head hadn't latched onto the threading quite right and was leaking somehow.
Bonus! My brother, using the MT3s I gave him said he was getting dry hits about every 3rd or 4th hit. I unscrewed the tank off the battery, noticing it was on extremely tight, unscrewed the atomizer head, and then screwed both back on, without forcing the tank as tight as it could go. Immediately I noticed that it had much better air flow and my brother reported that it had fixed the dry hits.
So as a first line defense just try disassembling and re-assembling your system!