I use a bottom coil clearo every day. When i fill it i never over fill. I leave at least 2 or 3 millimetres empty otherwise the liquid doesn't flow to the coil properly, something to do with the pressure in the tank. Also when the tank is down to about 3 or 4 millimetres of liquid it should normally start gurgling, again because of the lack of pressure in the tank. when this happens i'd hold some tissue paper over the tip and shake it, whilst holding it upsidedown, for about 30 seconds then use a q tip to clean out the tube. I vape with it for 5 minutes and then go through that shaking process again. After that i'll finish the tank with no more gurgling. I go through this process with "every" tank full of liquid. That's the routine and i'm used to it. That's how my bottom coil clearomiser works. If your gurgling and leaking all the time then i'd say you need to place a little cotton wool on top of the wick to stem the flow of liquid a little and it should stop the constant gurgling.