Hello, the overflow tank on the side of my Radiator will not stay full. My engine overheated about one and a half years ago, and ever since it will not stay full. When it overheated it warped the head and I had to get engine rebuilt. Waterpump and Thermostat were replaced at the same time. If I just let the car sit and idle for about 10-15mins the temp will start to go up. if I rev the engine to like 1500rpm for a min the temp will go back down. Also while the car is idling the Heater does not work, when I rev the engine the heat starts working again. Do I need a new Radiator? Has anyone had this problem.

I cannot explain where the water is going without an inspection, but the loss of heat is due to the coolant loss, which allows air in the system. The air also stops the circulation of the water that's in there at idle, causing the engine temp to rise. At higher RPMs the water will cavitate a lot, but will at least flow a bit. The thermostat will be open nearly al the time, but will flow enough to cool the engine.

Since you are constantly adding coolant, you have no heat at idle, and I'm confident this is your current problem. Adding coolant to the tank will NOT bleed the air from the system. Once the system id leak-free, it must be properly bled of air. This is a common problem with all cars- not just ti's.

Solution: you have to locate and repair the water leak first. Then completely bleed the system of air. Then you will have heat at idle, and proper engine cooling. Fix this before it gets hot outside, particularly at higher altitude, or you will be buying my nice, used engine!

Good luck!