1998 4.2 liter
i can drive the truck forever but it only moves a tiny bit, the needle never even reaches the middle of the gauge..farthest it ever reaches is where the little white line begins.
do i need a new thermostat?
i heard if i needed a new one my heater wouldnt work properly but my heat works nice and warm..

 

If you have plenty of heat, the t-stat is probably OK, but it wouldn't hurt to change it. It could be the temperature sensor/sending unit.

 

The gauges in these trucks are not meant to move with changes in conditions... Meaning, they are "idiot gauges".. You'd have to basically reach an overheating condition before the gauge will move to the 'hot' end.. Same with the oil pressure and volts.. They all have "idiot lights" with them too, so you'll see it come on too when the condition warrants.

I had a real water temp gauge in my 97 F150 and the stock gauge read the same from anywhere between 150* to over 210* on the real temp gauge. Never did see the stock gauge move even at 210*.

Change the T-Stat if you've never changed it, but your gauge will still read the same..

Mitch

 

That's all true, Mitch, but it should be running in the middle. After startup, it should slowly come up to the middle then stay there unless it overheats - then it jumps to the top.

 

Yeah, could be the gauge/sender itself.. Didn't read the post right the first time around..

If you have an IR temp gun, you could point it at the T-stat housing when it's warmed up and see if it's close to being normal temp of between 180-195.

Mitch

 

From my experience, the dummy gauge will sit in its parked position until 225*F, at 230*F, it will move off the thermostat icon, 240*F will be 3/4 way, and 250*F the top limit. 260*F will be the red zone and should engage the fail-safe where it shuts of the injectors and just pumps air.