On a 1998 lincoln

check coolant level,did you put right thermostat,could be air look,on top should be bleeder ,have to open to bleed the air,keep engine running.

Can not use any vehicle without a thermostat

The computer won't work correctly & you have
no use of the oxygen sensors or fuel contol untill
the vehicle is at the proper temp--197 to 210

It is under the cover that the top radiator hoseches to on the engine.

Just a stab at it................see if there's a vacuum or electric operated valve in the heater hose lines.Trace it out.The heater hose goes from the thermostat area at intake manifold thru the heater core,and back to water pump area. don-ohio

Locate the upper radiator hose. Follow it to the engine. Before it meets the engine, you'll notice that its clamped to a metal housing, usually mounted with 3 ten-millimeter bolts. This is the thermostat housing. Remove when engine is cool. Thermostat is inside. Remove old thermostat and replace ensuring the rubber o-ring aroung the outside of the thermostat if equipped. Good luck.

Water pumps ****!
Here is a link to an article that will tell you :
How to diagnose an overheating Lincoln

hit with big rubber hammer mine started to work after one good shot gets stuck from the rubber gasket getting hard so hit it

TRANSMISSION THERMOSTAT INSIDE TRANSMISSION ON VALVE BODY YOU HAVE A PRESSURE LEAK CHECK TRANSMISSION OIL COOLER LINES FITTING TO RADIATOR FOR LEAKS LOOK UNDER CAR WHILE IT RUNNING LOOK FOR FLUID LEAKS. YOU COULD A LEAKING TORQUE CONVERTER SEAL.

check your screen and window rubber seals by turning a hose on then water will always track to the lowest point

Then it is Possible Installers Utilized Wires from Hvac system for remote start and it may be Interrupting AMPERAGE with Temp Blend doors ? if not Try a Higher rated Thermostat such as 195 degree ratting.