The gurgle sound that you may hear now and then is a indication of a flooded coil. A flooded coil is a coil that has a bit to much juice currently wicked or soaked in it. This can happen from it sitting a bit to long with out being used, or a coil/tank being fired at to low of wattage.
But do not worry it is quite easy to fix this issue and determine what has caused it. All you would need to do is take a napkin of towel and cover the tip of the tank then carefully flick the tank in a down wards motion forcing most of the excess E-Liquid out of the tank. This should take care of the flooded coil but do make sure that the coil is being fired at the correct wattage. The wattage needed can usually be located on the side of the coil or packaging. Using the correct wattage will help keep the coil heating up correctly and keep up with the flow of E-Liquid that is absorbed into the coil.