I have a rover 25 1.4i and recently im having to top the water up every week! when my car is low on water when im driving i can see steam coming from the top of my bonnet where the coolant tank is and the temperature gauge going up between half and the red bit but once ive topped up its fine, runs fine, I do notice sometimes a patch under car every now n then and also brown stuff in the coolant tank, what is the problem with it? help please (ps my exhaust sounds like a boy racer one, if you know what i mean)