It seems you have a problem with radiator or the fuel regulator. I have had similar problems with my car before. I'd take it to a mechanic ASAP, as it might be dangerous to drive with such a condition. I am no mechanic but this is going to cost you. If you have a check engine light on, the diagnostic fee alone in reputed shops like firestone, midas will cost in excess of 100 dollars. If you know a local mechanic, your cost will definitely go down. If it is a very old car, i wouldn't bother fixing it.