I had my top radiator hose replaced as it was worn and had bubbly calcified stuff around the start of the hose near the clamp. Anyway, after it was replaced, now I have to fill up the radiator and overflow every time I drive the car. I have checked and there appears to be no fluid showing in the oil and there appears to be no visible leaks that I can see. Not sure what was done when the hose was replaced to cause this as this only started to be a problem straight after the hose was replaced.
There may be so much corrosion that the car is overheating and venting coolant out of the radiator cap. The heat sensor may have engough corrosion on it to not be able to tell car is overheating. Try a new radiator cap first.