2000 ranger overheating- unsure why
 

Hey guys, I have a 2000 ranger that has started overheating.
When I checked the coolant reservoir it was bone dry but completely clear, no debris or brown gunk.
Added more coolant and engine is still overheating, but as long as I keep the heat on high it’s fine.
Any ideas on what could be going on here?
Thanks

Stuck thermostat?

If Coolant is low in Radiator as well, there's a leak somewhere?
22+ year old vehicle; time to consider a CoolantSystem makeover?
New Radiator, Fan, FanClutch, Pump, Belts, Hoses, Clamps, ThermoStat, FLush+Fresh 50/50...