Very unusual problem with a rover MG ZR 1.4 petrol. Have had the head gasket done around 2 years ago and just this week had the fan, radiator an a new thermostat sensor replaced. Despite all this the car is boiling/drinkin a lot of water and constantly needs topping up. It also makes a weird gurgling/scrapping noise under the bonnet which seems to indicate the waters running out and needs topping again.