Engine temp gets cold on the highway

[DeRocha]

The fan clutch thing was irrelevant.. The fans job is to pull air through the radiator and cool off the Radiator. Like ipozestu said only a very tiny amount of engine cooling will take place by the fan blowing on the block. A working T-stat will open if it exceeds 195 F and close if it drops below 195 F. So it is really the only thing (besides a defective water pump) that could cause the problem you are seeing... The t-stat will have a purge hole to allow air to escape. This hole must be facing up (the highest point), or the cooling system will get air bound... like needing to bleed radiators in your house... Driving at a constant speed (highway) forces the water through the system at a constant pressure. Driving at varying speeds (city driving) causes the pressure to vary and oscillate through the system. This oscillation will help push/burp the air through the T-Stats.

 

[Billy177]

it is either in backwards or it is defective (this is not uncommon) the crese conrtol keeps the engine at the lowest possible rpms that along with the high flow of air from highway driving anyweakness in a thermostst will show up. if this does not occour if you drive with overdrive off than you have found your prolblem

 

[Hartman]

I did install the little air purge hole at the top, so I guess I did something right. The thermostat works great during city driving, even though it's in backwards, so I have to assume that the thermostat is working properly.

 

[99SportX]

Hartman-
You're the one who told me how to replace mine, but i paid attention to the one that was already in there. I end up doing a lot of things twice too, but they are usually things not as important as a thermostat. Sorry, I just had to say it.

 

[Happy94XLT40]

T-Stat or???

All is well but, yes always a but. My gauge is dancing around out of the blue. Its will be just as its always been and then bang in the middle and back down and up and then its all kewl again. Fan clutches. Nice shot Draper, remember an old 63 lincoln that did that. So just put a straight blade in of Electric. Or what? Oh t-stat was new over the summer. Really leaning to the fan.