DAngelo: I had this problem with my 97 Contour. The problem was that the water pump needed replacing. The rod in the center of the water pump was actually slipping, so sometimes the pump would be functioning and cooling, and other times not, so my heat gage would go up and down. Fortunately my mechanic had seen this before. Ford contours are known for their crappy water pumps you can get an upgraded pump with metal impellors instead of the stock plastic
Your thermostat is probably stuck closed you can pick one up at any parts store for about $12
Plugged heater core maybe. Maybe the thermostat. Coolant keeps your engine cool under duress. If the thermostat is stuck open, the engine is staying too cool. Your heat is run off of your engine temperature.
Fan not working Water pump not Working well enough Stuck Thermostat. Air Bubble in system Head gasket failure Radiator plugged or coated inside Radiator dirty or plugged stopping airflow
You need to double check that coolant, white smoke is a sure sign of a blown head gasket, especially when added to an overheating issue.
You can drive it a little but make sure there is plenty of coolant. Don't let it overheat, not even a little. If it's leaking too fast, you might end up having trouble if you drive it, but you should be able to put in some coolant and drive it to a shop.
There is a low level sensor in the side of the radiator. They do go bad.
the coolant level sensor is probably stuck it is on the bottom of coolant resivior most times all it takes is a tap with the handle end of the screwdriver on the side of the res where sensor is
Running your heater allows more cooling time for the water in the system. Check your water or coolant level to make sure you have plenty of water in the system.
a/c has a low charge
Check your coolant sensor for built up sludge, or the sensor may need replacement.
My guess is that the Coolant Thermostat is malfunctioning. It should be replaced. It is found, usually, at the engine end of the top radiator hose. Two bolts hold in place. A new one us about 7 or 8 dollars. I rate it as an easy fix. Good luck.
Make sure the engine is completely cool. Disconnect the hose at the water pump. Allow as much coolant as possible to drain out into a sealable container for proper disposal. Remove the hose from the radiator. If the hose is being stubborn in removal, carefully slit the hose around the fittings and peel it off. Replace with new hose and new clamps. Refill radiator with coolant. Allow engine to run for a couple of minutes to make sure there is plenty of coolant in the system. Add more if needed.