Ok, I've replaced my thermostat, waterpump, radiator, and radiator hoses and I continue to have this problem. The car runs very hot, near the "L" and it feels like the thermostat takes forever to open. When it does, the temp comes back down, but when I turn the car off, the reservoir is hissing, and overflowing with coolant. But I know the car is actually LOW on coolant cause my dash light comes on and the car has leaked coolant for a few days now. I wanna take the car to the track tomorrow, but I need to get this fixed soon. Can anyone help?