I have a Hotpoint fridge that's about 7 years old and came with the apartment. In the past couple of months, I have noticed an occasional "glug-glug-glug" sound, like liquid is moving around in there somewhere, when I close the refrigerator or freezer door. (There is no ice-maker in the unit.) The sound is not consistent, however, so I assumed the fridge was powering down at a certain point in its energy cycle and the coolant was moving around. When I first heard it, it was in the early-morning hours; it's currently happening around mid-afternoon, so it seems to be a cycle of some sort. The refrigerator temp is about 40F, and the freezer is still freezing things. Should I be worried?