Hey all.
99 sport I-6
I have a 195° t-stat and recently noticed that my temp gauge sometimes hovers between 150 and 180 while on the highway and randomly goes back to normal operating temp.
before I tear into anything, would you guys say it’s the t-stat that’s failing (getting stuck open) or the temp sensor?
the mopar sensor is $$ and I’d like to test it before replacing it.

 

You have a bad thermostat likely made in china.

Replace it with a Mopar brand.

 

Hey cruiser, just curious, I assume the electric fan is triggered by the temperature sensor as the thermostat is purely mechanical. Does the temp sensor control anything else besides the gauge and electric fan?

 

No. The thermostat controls the water temp in the engine.

 

I will search for mopar brand. I think they’re made in Mexico.

Also, does the temp sensor influence fuel delivery? I.e, if the temp sensor fails and is reporting temp values lower than actual, does the ecu dump more fuel?

 

The electric fan is controlled by the PCM through the fan relay. It turns the fan on based on temp from the Coolant temp sensor (in the thermostat housing) or when you turn on the A/C. So the coolant temp simply provides a temperature dependent resistance in the circuit that the PCM interprets to display the temp on the dash, control the electric fan, and manage engine operation.

If the engine does not get up to temp, the system may remain in Open Loop mode which does mean the PCM may increase fuel and idle speed. If this was due to a bad sensor, you would likely get a CEL.

You can test the sensor easily enough with an ohm meter.



One thing to mention. It's terribly cold out in many parts of the country. The extremely cold air flowing through the radiator at highway speeds my contribute to the low temp. Does it get to proper temp when driving slower (like local streets)?

 

Mopar stats are made in Israel.