I own a 1999 Saturn SL2 sedan. The car is losing coolant somewhere and results in overheating. Thus far I have changed the engine coolant temperature sensor and it signals the temp. gauge just fine. The cooling fan also works as it should. I replaced the thermostat, and the coolant pressure cap. I can not see any visible leaking out of any hoses or from the temp. sensor. When you park the car there is no coolant dripping to be seen. I can refill the coolant so that it turns off the low coolant light but within about 40 miles the coolant is back down to where the light comes on. Shortly thereafter, the engine temp. climbs into the red zone. I have tried to use the metal flake radiator seal and it has not helped. I am getting plenty of heat from the heater in the car as well. There are no fuses blown anywhere and I have replaced the fan relay just in case. There does seem to be some shiny oil/glazed looking stuff on the engine block, just below the temp. sensor but I'm sure that the sensor isn't leaking. I used teflon tape and made sure to insert it all the way in leaving no threads visible. There was only one time were we could see the coolant on the ground. It was the front left side underneath the bumper. But it only happened once and never again. Any ideas would be very helpful at this point. Thank you all. Brian