I have a 2008 Ford Ranger XLT with the 4.0L V6 SOHC engine, 4x4, 5 speed automatic, 4.10 axle gearing, and all that jazz
I live in Wisconsin, where the weather is extremely cold one day, and warm the next
Last week it was very cold, and my idiot light (CEL) came on, when I had it scanned it said the thermostat was stuck open, and I could tell because my temperature wouldn't go up to normal and I wasn't getting very good heat. Anyway, we cleared the code (I have no idea why) and right after I bought the part, it seems to have fixed itself, any possibility that it really did, or is it still stuck open?

 

It sounds like the thermostat may have stuck open. Just to play it safe I'd check the coolant levels in both the radiator and the overflow. If its ok, I’d replace the thermostat at your earliest convenience.

 

X2 on replacement
Sounds like a gummed up stat, take out the stat, flush the system and replace with new stat and antifreeze.

 

Ok cool. I had purchased the new thermostat and gasket for $20 cost. I will have my mechanic do it because I am mechanically inept (lol). Plus somehow I can see myself forgetting to put the thermostat in correctly, or using incorrect fluids. Thanks all

 

You may have one of those t-stats that stay open when they fail which is a good thing on saving your engine. Like everyone else says, get it changed fast because your engine will not be running as best it should and the mpg's will suffer.

 

I didnt know you can get a CEL on a open thermostat.

 

yea because the engine will never reach normal operating temp

 

I understand that but it doesnt make sense how it could read it. Unless you have to drive it a while then it sees its still cold. I'm guessing one of the sensors on the bottom thermostat housing has to do with it.

 

yea there are 2 ECT sensors...one for the guage and one for the PCM so it knows when to switch from open to closed loop

 

Alright that answers my question

 

HA! It has happened again, but upon further inspection, have found that the previous owner installed a fail-safe thermostat which is designed to allow continuous flow upon any failure that occurs. So, basically I can get the new thermostat with fail-safe for $50 or just leave this one in, since I always idle the truck long enough to defrost windows in the winter, also considering the AC compressor runs when you turn on the defroster