Strange issue with Temp sensor on 97 4.6

[dgalvin66]

The temp gauge was jumping to max and the oil pressure was also jumping to max at the same time. I found that if I disconected the temp sensor the oil worked just fine.
I replaced the temp sensor and now it does not read anything but the oil is working fine.
Not quite sure what the problem is. Only thing I can think of is that the new sensor is bad??
When I start the engine I do see the temp gauge do its check like it should then the needle drops all the way down like the key is off and it stays there.
I know it is not over heating since there are 2 temp sensors and it is not going into limp mode and not showing any symptoms of over heating.

Does anyone have any ideas of what to check before I go thru the hassle of changing it out again?
Thanks

 

[stamp11127]

IAT/ECT SENSOR VOLTAGE AND RESISTANCE SPECIFICATIONS
Temperature Engine Coolant/Intake Air Temperature Sensor Values
.°C --°F----(v)----(K ohms)
120--248---0.27---01.18
110--230---0.35---01.55
100--212---0.46---02.07
090--194---0.60---02.80
080--176---0.78---03.84
070--158---1.02---05.37
060--140---1.33---07.70
050--122---1.70---10.97
040--104---2.13---16.15
030--086---2.60---24.27
020--068---3.07---37.30
010--050---3.51---58.75

If you have a voltmeter or multimeter you can check the resistance without removing the sensor. The resistance should be close to what it shows in the chart for the given temp. If it is then you most likely have a connection or harness problem.

 

[dgalvin66]

Ok then I should run it for a bit with it unplugged and check the resistance on the sensor. I will give that a try here in the next day or two.

One other thought I had was that when I changed the sensor I lost some fluid but not much, could this have caused an air pocket in the system at that point keeping the coolant from coming in contact with the sensor? If so how can I burp the system?

Thanks

 

[stamp11127]

If you like working on a hot engine then you can run it some. Me, I'd prefer a cold engine. The chart gives values for low to high temps. If air was stuck at the sensor you should still get a reading that would increase as it warmed up. It wouldn't be accurate though.

The only bleeding instructions are to idle with the heater on and check for heat once it is up to temp, refill the tank as needed when cool.