It is pretty cold here in Northeast PA now. My truck doesnt really want to get warm. It comes up just above the C line on the temp. guage. Last year, the heater in the truck would about burn me out of the cab before I got to work, now its just warm in the cab. Its an 02 F150 with a 4.6L. I am thinking it may be the thermostat. If the thermo. fails, does it fail in the "open" position?

 

It can fail open or shut unless it is one of those designed to fail in the open position. Odds are that it is the t-stat. Pull it when the engine is cold. If it is open toss it and put a new one in.

JMC

 

yeah most likely thermostat stuck open. here on the eastern shore alot of people don't even have thermostats because they are so worried about overheating then they dont understand why they dont get heat.

 

My stat did the same, went only so far because it was stuck open as it should. It was only a matter of time before the CEL came on. Happened around this time too when it failed. Easy fix, cheap too.

 

What did you notice that your temp guage would read? My comes about 1/4" above the Cold mark and then sets there. It used to ride about half way between cold and hot (i think).

 

Temp gauge rides ~1/2 way when warm, unless you have installed a really low temp stat ~160 deg F.

Here's a quick check for stat failure. Drive your truck until the temp gauge no longer increases. Get out and block off the front of your radiator with a piece of cardboard. If the temp gauge increases with the radiator blocked, you most likely have an open stat.

 

Yeah, I havent tried that yet. But I am 99.9% sure that the thermo is shot. Truck has 123K on it and I had to replace the hoses and such already. Like a dumb ****, I didnt do the thermo while I had the hoses off the motor.