I have a 1994 Ford Taurus GL with the 3.8 liter engine and 100,000 miles. I recently replaced the radiator due to a crack in the side tank and had the mechanic replace the t-stat at the same time. The motor was never overheated. One month after the replacements, the temp gauge on the dashboard started to fluctuate. In the morning or just when it is cold and driven for about 3 miles the needle would react normally and then begin to climb almost into the red. (Makes it to the vertical line on the hot side of the gauge) The engine does not seem to be overheating at this point. No heat in the cabin. The electric fan turns on and after about 2 minutes the needle drops down to midway or sometimes lower and heat is felt in the cabin. Then the cycle begins again. As the needle rises, I loose heat, fan turns on, needle lowers and heat is produced. This will happen for about 15-20 minutes or about 10 miles then suddenly everything is working properly. Great heat and the needle is in the normal operating range and steady. I had the mechanic re-replace the t-stat thinking the "new one" went bad. Same results. Assured that all the air is purged out of the system and the coolant is full. When cold, I notice I can add about 3 cups of coolant but each time I do this, the next time I check the reservoir when cooled down, it is a little fuller so I am assuming that while cooling down the freeze in the reservoir is not being drawn back into the system to maintain it's fullness. I have checked the water pump and it is dry and solid. No leaks on the ground under the car and the heater core seems fine as well due to the lack of wetness on the passenger floorboard normally associated with a leaking heater core. The system also is holding pressure for hours. Today I replaced the threaded in, 1" nut size "Coolant Temperature Sending Unit" which is located on top of the t-stat housing. This sensor has 2 wires going into it's plug, Light Green/Red and Gray/Red. I still have the same problem. What else can be causing this issue? I am a mechanic myself and am stumped. Please help if you can. Thank you for your time.
have the same problem?
Wednesday, April 6th, 2011 AT 11:22 PM