97 taurus overheating after new thermostat

i recently lost heat in 97 taurus with 204000 miles. had a new temp sensor put in because temp gauge was not working. that didnt help either problem. put in a new thermostat last nite and have heat like car was brand new, problem is by the time i drove it home 8 miles it had overheated. when i just let it run in the driveway or drive in town it is fine, but when i take it out on highway coolant is coming out of the resvoir cap. by the way, even with the new t-stat the gauge in the car still did not move at all. any suggestions. thanks

Are you sure you installed the thermostat in the right orientation? If you put it in backward, it will have to get VERY hot before it might open. If you installed it without positioning the jiggle valve correctly, you might have a large air pocket in the system would could cause the overheat condition as well.

Even though you mention coolant comes out the overflow tank, if the thermostat is closed the expanding coolant could be forcing its way through the lower radiator hose and forcing coolant out the overflow.

How hot is the upper radiator hose (careful!) when the car is beginning to overheat?

-Rod

rod,
put the t-stat in the same way old one came out, so i think it is ok. think i found the reason for the overheating. after topping off coolant, didnt let car run long enough to see how much to replace with and might have come up short. also just found out the housing was cracked for the t-stat. new one on the way tomorrow. any idea on the temp gauge not moving? thanks for replying.
dave

Do you have access to a scan tool with a data stream function? If so, you could check the datastream for the coolant temp to determine if the guage is reporting similar to what the PCM thinks the coolant temp is. I'll check my service manual for my 1998 to see if the gauge is driven off the same sensor as the cooling fans, etc.

Is the guage stuck on hot, cold, in the middle, or where? I think open circuit the guage will read all the way cold.

-Rod

The coolant temperature SENDER for the GAUGE is located above the left side of the engine block, near the thermostat. The engine will also have an engine coolant temperature SENSOR that is also mounted above the left side of the engine block near the thermostat, but it appears is forward of the sender. The sensor is used by the PCM to adjust air/fuel ratio, etc.

It appears open circuit of the sender should give a "Cold" indication and short circuit would give a "Hot" indication.

If you'd like me to e-mail you the diagnostic procedure for the sender, PM me with an e-mail address that can accept attachments. You'll need a 275 ohm and an 18 ohm resistor.

-Rod

The coolant temperature SENDER for the GAUGE is located above the left side of the engine block, near the thermostat. The engine will also have an engine coolant temperature SENSOR that is also mounted above the left side of the engine block near the thermostat, but it appears is forward of the sender. The sensor is used by the PCM to adjust air/fuel ratio, etc.

It appears open circuit of the sender should give a "Cold" indication and short circuit would give a "Hot" indication.

If you'd like me to e-mail you the diagnostic procedure for the sender, PM me with an e-mail address that can accept attachments. You'll need a 275 ohm and an 18 ohm resistor.

-Rod
rod,
gauge reads well below C. doesnt even move is sender something i can replace myself? sent you my email address.
thanks
dave

Unfortunately my service manual doesn't seem to explain real well what is involved in replacing the sender. That's hopefully because it's as straight-forward to replace as it seems. From the diagram in the manual, that shows the approximate location, I would expect that you unplug the old sender, have the new one close by, unthread the old one and quickly thread in the new one before too much coolant leaks out. The new sender should have thread sealer on the threads already.

Once you get the new one snugged up and plugged back in, you will want to run the car to operating temperature, top off the coolant level as needed, and verify proper operation of the guage.

You may want to run through the troubleshooting procedure that I'll forward to you tonight when I get home first though in case the problem is in the guage or wiring rather than the sender.

-Rod

thanks rod,
hopefully this will solve my problem.
dave

rod,
just put on the new housing and a new thermostat, since the one car quest gave me the other day was for a '96, no wonder i cracked the housing trying to put on an o ring with the gasket and t-stat. i picked up a hanynes book today for the taurus so maybe i can do some of this stuff myself. thanks for all your help. looking forward to getting the info tonite.
dave

thanks to shorod for all the help. replaced the coolant sender today and the gauge took right off. all seems fine now. thanks again.

Great job! That's nice to hear. You're welcome.

-Rod