Heater would make a gargling sound like there was air in the system and there was no heat and the temp gauge would rise towards the hot level. Fortunately it was cool out and the ramp air kept the engine cool. Called KIA service and the mechanic told me to check the coolant overflow tank. It was empty. He said it probably has a crack in the bottom that is was a known problem. Did not see any coolant on my garage floor so I was puzzled (you could eat off my garage floor). Mechanic said you would not see any leak as it only leaks when warmed up and leaks onto the exhaust manifold so it would evaporate. Of course it happened 1500 miles after the 60k warranty. So I had to eat the cost of the part @ $95 which wasn't too bad.