90 ranger 4.0 ltr, i replaced temp sensor and sending unit, the gauge, and thermostat, tested old and new thermostats and both open. Gauge still reads over red line hot... any ideas?

 

Is engine HOT?

Does heater blow HOT?
If not then there is air in the system

 

Hey Ron ty for reaching out, how would u go about getting the air out if there is?

 

Cold engine
Remove radiator cap
Remove either heater hose at firewall
Pour water/coolant into radiator until it comes out of both heater core and hose, put hose back on

Drive with heater on should warm up if there is no air in the system
If it starts to overheat, see if heater is getting cooler, if so you have a blown head gasket or cracked head, this will cause MORE AIR to be pumped into the cooling system

If heater is still hot and engine overheats then bad water pump or radiator

 

So I did what you said but I think I need to re-ask this question differently. I replaced all sensors and gauge because the last gauge wouldn't move from cold. But now the needle doesn't go down to cold even when engine if completely off. Like in the picture, when I turn the key on but not start it the gauge goes way above hot and stays there.

Key off

Key on not started, but does this even when started

 

The temp sender wire is grounded

The temp sender on the engine will have one wire(temp sensor has 2 wires)
Sender is 12volts, sensor is 5volts, so NOT interchangeable, but they "look similar"

Unplug the sender wire from sender
Turn on the key
Gauge should stay on cold
if not start tracing the sender wire, it is shorted to ground somewhere, you can leave the key on while looking and check gauge now and then to see if needle has dropped to Cold

If needle is on cold with wire unplugged, then new sender is bad OR someone sold you a sensor instead of sender

 

Awesome, I went and messed around with the wires and the temp sensor wire broke. I had to open up the wiring harness to find it. Found it and fixed it. Thanks again Ron.

 

Good work

Thanks for the update