I have a 96 F250 SC, LB, 460 auto. I've only owned the truck for about a week and my engine coolant temperature guage hardly moves off of "C". After about 1 hour of around town driving, empty, the needle is in the "normal" zone, but barely past the first line (you have to look rather closely to tell that it has moved). I initially thought that the guage was broken but seeing that it does move leads me to believe that either:

1. The radiator is oversized and the coolant won't reach the middle of the "normal" range unless I'm towing, or
2. My temperature sensor is not functioning properly

Is this normal for this engine set-up? If not does anyone know how to resolve the problem?

Also would a bad sensor (not telling the engine it has warmed up) cause the idle to remain high?
Thanks
MP

 

Your thermostat may be stuck open not holding coolant in the motor long enogh for it to heat up.

 

Hi and welcome to FTE

I agree, it sounds like you either have the wrong or bad thermostat in the engine.
It should have a 195 degree thermostat.
Running too cool will cause premature engine wear because the pistons and rings don't expand like they would if it was up to heat.
Also on a fuel injected engine, it will run too rich because the computer doesn't see that the engine has warmed up to put it into the normal closed loop.
Jimmy

 

Thanks for the timely responses and sure enough, just as you both had suspected the thermostat was the problem. I put the 192 deg thermostat in and it comes up to operating temp and holds steady. However, interestingly enough, the thermostat was a problem because THERE WAS NO THERMOSTAT in my truck. This struck me as odd since I personally could not think of a reason to remove the thermostat. But the previous owner must have removed it, or forgot to replace it. Is there something I should know here? Is there a reason to remove the thermostat? Would someone do this if they wanted to "cover up" some problem? Or is that an acceptable configuration?

 

I think people do that to cover up a problem like running hot. Or .....I can't remember why they used to remove them. It is NOT an acceptable practice in my book. As you have learned, there has to be something in there for 2 reasons. It holds the coolant in the motor so that the motor can get up to operating temp (quickly) and to allow time for the coolant in the radiator to cool.

 

Step is spot on !

Always run a thermostat.