I have a 92' Honda Accord (actually my mother in-law does) While driving a week ago, 150 miles into the trip, the temp gauge was at operating temp and with every mile traveled the gauge got closer and closer to the Cold Line, until eventually it was reading all the way cold.

Heat works great! I noticed that if I turned the heat off the temp gauge went back to operating temp. Any Ideas? Temp sensor?

 

Stuck-open thermostat?

I think if it were a bad sensor, it would stay cold when you turned off the heat.

 

That is a very good question. Did you check the coolant level?

 

x2

 

Open the radiator cap & check coolant level in the actual radiator. (Or squeeze the radiator hose & listen for sloshing = air.) If the radiator cap is bad, it's possible for the overflow reservoir to be full while the radiator is very low.

 

Well today I am performing a flush and thermostat change, I will let you know how it goes. I'm not sure I understand why a stuck open thermostat would cause this. If a thermostat is stuck open the car would have alot of trouble reaching operating temperature. The car makes it to operating temp and stays there. Thanks guys I will update later

 

Well 2 hours into the flush proccess and replacing of the thermostat. The old Thermostat was stuck open (Foot In Mouth) anyway I will be finished in about 20 minutes and will test drive it and update in the morning. Thanks

 

dont wanna say we told ya so, but... we told ya so :P lol... hopefully that'll fix your problem...

 

Sometimes the T-stat just sticks occasionally. When it's actually cooled down (overnight?) the T-stat will close. Then when you drive it opens & sticks there. Has to really get COLD before it closes.