Thermostat went out last Sunday. What is causing this.


Asked by Jan 17, 2016 at 08:19 PM about the 1999 Ford Explorer 4 Dr XLT 4WD SUV

Question type: Maintenance & Repair

My thermostat went out last Sunday. I put in a new one on Monday and
everything was great until I went out to warm up my vehicle this morning. As
soon as it got warm the temp gauge spiked again.  The heater was blowing
out cold air.  What is causing this.

3 Answers


Are you sure you put in the new thermostat in the right direction?


yes. I installed the new one identical to the one I took out. I am wondering if I should have went ahead and changed the coolant temp sensor also.


Is the coolant old. If a 50/50 mixture is not maintained it will overheat. Get the engine up to operating temp and feel both lines leading to and from the heater core. If one is hot and the other cold, there is a blockage in the core.

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