In my 2014 vauxhall corsa, there is a watery sound happening. Not a dripping, but a travelling/gurgling sound - like when you first turn on the radiators at home and the water moves through the pipes. It's a newly purchased one, but I was told that they had just replaced the water pump before I got it. Someone at work said that it might be air in the coolant, and I should watch out for overheating. But I haven't noticed any problems yet. Is this anything to worry about?