Hi I'm new sorry If the post is out of place or something.
Okay just bought a old work truck for 500$, it is a 98 explorer 4.0 efi auto trans 4x4 219k on it.
It starts every time cold or hot, runs / drives okay needs suspension and wheelbearings ect and tune up but my issue that's puzzles me is.

THE temp guage never moves much it's cold in ks now so it barely moves. In the summer it moved more but not enough I feel. It never over heated in summer or now. It was leaking coolant but found the source the radiator cap was wore out. Got a new one and system regained pressure when hot.
We get heat out of the vents and defrost vent for windshield but it's only so so warm.

Possible problems

1.stuck open thermostat?
2.coolant temp sending sensor faulty ?
3. Belt fan is just making motor run cold because its 20 to 30° in ks.
4. Water pump is running bad( paddles inside it are rusted and falling apart.?)
5 ?

 

I would suggest you start with just replacing the thermostat and gasket
A 192 or 195 should provide good heat

Sending unit should not affect coolant temp
If motor doesn't sound excessively noisy I wouldn't suspect fan problem
If water pump had a problem you most likely would see some overheating. Not knowing past maintenance history former owner might have removed thermostat due to some pump problem, so take things one at a time and see what you get.