If you see my previous question just got the car a few days back and it overheated very after a few miles, they won't take it back, instead they are helping to fix it, I just bought a radiator and replaced it today, it seemed that the previous was fixed and when we cleaned it with acid it crack and poured water like a water fall. Now after changing the radiator, we tested it parked with the heater on and the car did not overheat. So we took it for a ride with the ac on and after 2 miles +/- the temperature jumped from mid to red in a second. The mechanic doesn't know what is it, he thinks might be the thermostat so I got a new one, he wont be able to put it on until tomorrow. I asked someone else and he said it sounds like an air pocket since is pushing water and air up through the reservoir lid. Some else said is a bad head that is getting worst by the minute, but the mechanic says that it doesn't show water on the oil and is not smoking and the car has lots of power like new. Another comment was that the fuel pump was bad, but the mechanic working on the car says that water is moving fine... we were hoping that it was the radiator. What can I do or should do?