Thermostat or not????

[dleague]

Well I have the 04 Explorer 4.0 V6 EB edition. I am baffled by a potential thermostat issue? I drive the explorer some days to work in the morning around 530 AM. Its nice and cool outside. After about 10-15 minutes of driving it on the highway the temp gauge inside starts to rise. I can usually get it to go back down after throttling the motor a few times, around 2-3X (letting off the gas and giving gas slightly). Then it goes back down to normal operating temp. Never happens again all day long. Weird thing is that it only happens in the morning when its cool and only happens once a day, but always happens when I drive it to work. The wife drives it locally for about 10-15 minutes taking the kids to school and it doesnt do that at all. Im baffled. Im wondering if it is the thermostat or maybe a sensor? I dont mind changing the thermostat but if thats not the problem then dont want to mess with it. Any thoughts?

 

[pet575]

I'd start by changing the thermostat-cheap and easy. Sounds like it might be sticking for some reason.

 

[DavidBlaine]

Have you ever changed your coolant? Could be getting gunky in there. A good flush probably wouldn't hurt if you haven't done it in a while.

David

 

[Exproblems]

Im wondering if it is the thermostat or maybe a sensor? I dont mind changing the thermostat but if thats not the problem then dont want to mess with it. Any thoughts?

I read in here a while ago where someone mentioned the temp sensor was faulty due to scaley, gunked up old coolant. The gunk built up on the end of the sensor that sits in the coolant flow and was causing faulty temp readings. Having said this, you still could have a faulty t-stat or a bad sensor. Is the coolant level full right now? Make sure the coolant level is full in the Expansion tank. Low coolant level can cause temp problems as well. If your coolant is currently full, then I'd say you need to start with the cheapest fix and that would be the t-stat/o-ring seal (about $18). T-stat housing bolt torque is 89 inch lbs and a 2004 V-6 Explorer t-stat temp range is 194 to 210 degrees. It's an easy fix. Not sure what the sensor costs, but I would think more than a t-stat. If your coolant is old and funky, flush and fill it with new. There should be posts in here on how to change the temp sensor and do a coolant flush and fill. You can find them using the search box, just type a question into it.

 

[tower]

I'd start by changing the thermostat-cheap and easy. Sounds like it might be sticking for some reason.

This

 

[esclamada]

Have you tried purging air from your cooling system? It's easy to do (it might help or not)
Just leave the expansion tank open, turn on your car and set the Heat and Blower to MAX. After 5mins squeeze the big hose between the radiator and thermostat (you should feel warm coolant flowing in this hose and squeezing will move air out) after 15-20mins turn off the engine and close the expansion tank. If it doesn't overheat after this then it must be air trapped inside your cooling system.



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