Chrysler Repair: Town & Country 2003: Coolant is overheating, losing coolant, upper radiator hose

Question
Hello:  Van has a 3.3 engine with 100k miles.  Temperature gauge started to beep, but car was running as usual. I turn engine off for a few seconds and the continuos beep stopped.  Couple of miles later the beep came back. I did same thing as before. This time after a few minutes, temperature came back to normal. When I arrive to school, I looked under the hood and there was a little freon spill with not noise of water boiling. I check the freon level, it was at the minimum level.
Question: Is it the thermostat, the pump, temp sensor. I know where the pump is, but where is the thermostat and temp sensor. Sergio in Dallas

Answer
Hi Sergio,
Did the cooling fans come on when the temp moved upscale and the warning beep sounded? If so, then the temp sensor is o.k. If not, then I would check the resistance of the temp sensor and also the operation of the fans. The temp sensor is located next to the thermostat housing and it has a 2-wire plug (wire colors black/light blue, tan black). If you lift the tab gently on the plug you will access the pins of the sensor. When the engine is cold the resistance should read 7,000 to 13,000 ohms and when it is warm (about half scale on the gauge which works on a different sensor) it should read 700 to 1,000 ohms.
To check the fans, turn on the air conditioning which should start the fans.
The thermostat housing is the hemispherical-shaped manifold on the top of the engine to which the upper radiator hose it attached. You can remove the housing and lift out the thermostat and put it in a pan of heated water with a thermometer and note whether it opens when the water reaches about 195F.
The pump is probably working, so long as it isn't leaking.
Where did you see the coolant leaking from? That may be a clue as to what is wrong. Are you losing coolant regularly? Do you see white smoke coming from the exhaust pipe when you start the engine in the morning from cold?
The next time you start the engine, watch as it warms up to notice if there is air bubbling into the coolant overflow/reservoir bottle very quickly before the engine fully warms up which would be a sign of a head gasket leak. Also, check to see if the oil appears normal, or cloudy/frothy.
Tell me what you observe and maybe we can resolve this situation.
Roland