I got the waterfall behind the dash sound too. It sounds like those little in home waterfalls people put in their rooms to fall asleep haha. But the thing is, it doesnt overheat a bit, the coolant never rises or falls and is clean, doesnt blow a lick of smoke(assuming it cant be a headgasket???). The only thing I can say about it is that the heater in the car doesnt blow hot air sometimes when I turn it on... Just a bubble?