Check the radiator fan operation.
The thermostat is located on the back of the engine. It is located close to where the radiator hoses attach to the engine.
there are two hoses coming from the radiator. the one on the bottom has the thermostat at the end near the back of the engine.
Only if they are bad !
Try replacing the radiator fuse relay
on a 1993 4.9 it is just to the left of the thermostat where the radiator hose and heater core hoses go into the thermostat it has a couple of wires running into it.
There should be two hoses connecting your radiator to your engine. Follow the lower of the two hoses from the radiator to the engine. The hose will be connected to the thermostat housing near your distributor, towards the back of the engine. Having reasonable workspace on the passenger side of the vehicle's engine compartment will help while replacing the thermostat there are two hoses coming from your radiator. where the top one connects to the motor is the location of the thermostat there is a coupler there with two screws take that off to reveal the thermostat also you need to replace the temp sending sensor located right next to the sensor has wires coming from it ask someone to show you hard to explain Follow the big upper radiator hose down to the engine. The hose usually is attached to the thermostat housing. its the lower hose its in the cast aluminum assy under and slightly behind the distrubutor.
Check your coolant levels, and check your thermostat - it may need replacing. Also check your heater hoses to ensure they're not leaking.
Do the electric cooling fans kick on?
Hard water, and calcium can build up insite the hoses and get released in chungs during the flush process. These pieces can get caught in the thermostat and cause it to fail. You can try removing the thermostat or just replace it as it is an in-expensive part. You might consider re-flushing the radiator as more calcium might hit the thermostat after replacing it.
Make sure antifreeze level is not low. And also "bleed" air from the cooling system. Look for bleeders where water hoses enter the engine. (might be one right on the thermostat housing).
Probably the hoses for the power steering pump or fittings on the hoses. Try replacing them first. They're not that hard to replace an relatively cheap.
test flow in and out of heater core it may be plugged or need replacing, if it is not plugged up check temp controls, may be stuck in vent or a/c setting.