T-Bird Overheating

Help. The coolant overflown bottle om my T-Bird Keeps filling up and the car starts to run hot. I beleive that the cooling fan is not coming on at the proper heat range. What sensor should
I replace. The Engine Coolant Temperature sensor or the Coolant temperature sending Unit. I beleive that the sending unit controls the temperature guage on the dash but do not know what signals the fan to come on. Any help would be apperciated.
Thanks
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snipped-for-privacy@bellsouth.net wrote:

The problem is likely not a sensor. The fan is controlled by the PCM. Does the fan run? If not the suspects would be the fan motor or relay. What year is the car and which engine?             Tom
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Yes the fan runs. What is the PCM ? I have taken out the thermostate and am running without it. So why would the oveflow bottle fill up all the time. I still think that the fan is not coming at the proper heat range. The radiator and water pump are only 1 year old. So I don't know what the problem is. The raditor cap is new as well. I thought that the cap might not be the right pressure and letting the coolant seep too soon. What is your thoughts.

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javatek?@usa.com wrote:

The PCM is the Powertrain Control Module (main engine computer). It is unlikely that the fan is coming on at the wrong temperature. The ECT (Engine Coolant Temperature) sensor tells the PCM what the coolant temperature is. If it were out of range enough to cause overheating (and excessive cooling system pressure) you would also have other severe drivability concerns. You didn't state the engine size but I'm starting to suspect it's a 3.8L. Remove the radiator cap and top off the radiator. If you see bubbles with the engine running the problem is most likely blown head gaskets. Look to see if you have bubbles coming out of the radiator neck while it's running and check back.
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If you run a koeo self test you'll know if the fans work or not because the fans will either work or they wont. If there is a electrical problem with the fans you will get codes. No codes go to the basics of cooling system diagnosis.

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