I have a 2001 Buick Century that is always running out of coolant. It never comes out from under the car and we feel it is going in to the engine and has been in the oil tank. We have had it to mechanics many times and they can't find anything. They have replaced many things but it's still doing it. The car never steams and overheats but the heat gauge starts going way over when the coolant is low. Maybe you can give me some ideas about what to do. Could it be the radiator? The mechanics here didn't think so. I would appreciate any help you can give me.