That is a failed water pump. That hole is there for the pump to leak when its shaft seal goes bad.
You can uninstall thermostat and install new thermost under air filter and look coolant hose by sensor gang. I did my own car.
(1) Remove the right front wheel. (2) Then the wheel body dust cover (two screws). (3) The thermostat housing is now viseable 3 screws secured the thermost to the engine block.
Remove the thermostat from vehicle. Heat up a pot of water on the stove, insert thermometer in the water along with the thermostat, be sure to fill pot of water to cover thermostat. When temp reaches operating level (180 / 195 ) should be able to visually see thermost open. Get tongs and pull thermostat out of water. When it cools down you should see it close.
The Thermostat on a 98 {as my truck} through 03 is locate on top just in front of the engine valley where the return hose connects to. Simply unbolt the the filler neck, lift {rubber thermostat seal may break} and the thermost will be in the hole. Clean any excess seal debris off, replace, rebolt, and your on your way. Erik
gasket or o-ring. always need one or the other
www . ford parts . com ( no spaces ) only shows ( 1 ) engine thermostat for a 1992 Ford F-150 with the 302 cubic inch V8 engine : ( Motorcraft RT-1105 / 192 * F )
The copper pellet opposite the spring end goes into the engine.
There is no reason to ever bleed a cooling system.
Its too hot engine temp should range between 180 & 195 depending on which thermost you have.
It goes to the temp gauge which is usually screwed in the head between the manifold on the drivers side, or into the thermost housing on the intake manifold.
Try your voltage regulator
No . You should never operate any liquid cooled engine with out a thermostst it will never get to opertaing temp. On a carbengine this will prevent the choke form opening and on a fuel injection injection this will prevent the processor from going into loop.