2002 sentra engine temp raising after a few miles. Radiator fan tuns on high. I need to turn the heat up high to reduce the engine temp. Water level is fine and heat works.

It sounds like you have an air lock in the coolant system . loosen of a high point hose and let the air out while keeping an eye on the water level in the radiator.. engine temp sensor will only send a signal to the CPU to adjust the fuel mixture and turn the fan on. It is not a temp gauge sender unit.

Could be radiator or air lock.

Maybe your radiator is clogged.

you could have an air lock would bleed heater hoses

Have you verified that system has been "burped" of air? That the fans kick on? Check radiator hoses for kinks. You can try running without the thermostat to see if that helps and can identify if the thermostat could be a problem. You may need to check your coolant mixture too.
Sounds like you have reduced flow or restriction in cooling (heat exchanger) as it runs fine at cooler temp but can't keep up when it gets warm.
New parts don't always equal working fine parts.

Check Thermostat
wires and last the fan one of them might be telling you is shutting
down completely this cars will last forever if you maintain correctly ,i had
a 91 nissan altima drove from LA to Ensenada every weekend
no problems at all.

u may need 2 get your radiator checked make sure its not blocked inside&restricting the flow

CHECK COOLANT FAN FUSES AND RELAYS. CHECK COOLANT LEVEL.MAKE SURE ITS NOT TOO LOW BECAUSE IF COOLANT TOO LOW . BY NO COOLANT AROUND OR COOLANT SENSOR NOT SUBMERGED IN COOLANT COOLING FANS WONT TURN ON.MAKE SURE YOU HAVE 50/50 ANTIFREEZE AND WATER. CHECK FOR CLAPSE RADIATOR HOSES.CHECK RADIATOR HOSE AT WATER PUMP.IF HOSE LOOK CLAPSE REPLACE IT AND BLEED COOLANT SYSTEM.IF EVERY THING HAS BEEN DONE YOU NEED ENGINE BLOCK FLUSHED OUT.HEATER CORE ALSO COULD BE STOPPED UP.A VERY HIGH MILEAGE ENGINE WILL OVER HEAT.OLD ENGINE LOSES COMPRESSION AND HORSE POWER.PUTTING MORE LOAD ON THE OLD ENGINE WILL MAKE IT OVER HEAT.IF COOLANT LEVEL IS LOW.BLEED COOLANT SYSTEM.START THE ENGINE LET IT IDLE FEW MINUTES WATCH THE COOLANT TEMPERATURE GAUGE.WHEN TEMPERATURE START RISING.TURN OFF THE ENGINE LET IT SET FOR 20 MINUTES.TAKE A LARGE RAG PLACE OVER RADIATOR CAP ON COOLANT EXPANSION TANK SLOWLY OPEN RADIATOR CAP JUST A LITTLE TO RELEASE A LITTLE PRESSURE AT A TIME.DONT OPEN CAP RAPIDLY OR YOU WILL GET SCALDED.ONCE THE RADIATOR CAP REMOVED.IF COOLANT LOW ADD MORE COOLANT IN THE THE COOLANT EXPANSION UNTIL YOU GET TO THE COLD MARK.REPEAT THIS PROCEDURE START ENGINE LET IT RUN UNTIL TEMP GAUGE START CLIMBING A BIT DONT LET CAR RUN TO OVER HEAT JUST IDLE UNTIL TEMP JUST START TO RISE.THEN YOU TURN OFF ENGINE. WAIT 20 MINUTES.THEN USE LARGE RAG OPEN RADIATOR CAP LITTLE AT A TIME. DO THIS PROCEDURE UNTIL THE COOLANT IN THE EXPANSION TANK STOP DROPPING. THEN ALL THE AIR IS BLEED OUT THE COOLANT.WHEN COOLANT LEVEL STOP DROPPING, WHEN YOU DRIVE CAR AROUND.AND TURN OFF ENGINE.WHEN ENGINE OFF CAR SET FOR A WHILE KEEP CHECK ON THE COOLANT LEVEL IN COOLANT EXPANSION TANK. THE COOLANT LEVEL SHOULD BE AT THE COLD MARK IN THE EXPANSION TANK.MAKE SURE COOLANT IS IN THE EXPANSION TANK.IF NOT AIR WILL DRAW IN COOLANT SYSTEM. CAUSING ENGINE TO OVER HEAT.IF BLEEDING AIR OUT THE COOLANT SYSTEM DONT HELP AND COOLANT FANS DONT TURN ON YOU HAVE PCM PROBLEMS.

I think you could be right about there being air trapped in the system.
Or the heater core(radiator) is plugged.
Either way you need a pressurized radiator coolant pump to put the coolant in without air being trapped.
Although,i have seen it done by jacking the vehicle up high enough that the radiator was now higher than the heater core level, and then the coolant was put in.
But this is dangerous to try.

One of the common things that gets missed at times is the radiator is down in cooling antifreeze. The car will act as normal during the warm up cycle and then the temperature guage will rise and then it will slowly come back down as the thermostat opens and/or the electric cooling fans come on. In actuality the engine is overheating, but it is not boiling over. The level of abtifreeze is at just the right level of lowness that you experience this phenomenon. After the engine cools off , (DO NOT REMOVE WHEN HOT - YOU CAN GET SCALDED WITH BOILING WATER/ANTIFREEZE)), remove the radiator cap and check the level within the radiator and also the antifreeze reservoir level. You can buy a 50-50 mix of antifreeze and water that is ready to put into the radiator. If the level in both the radiator and reservoir are correct, you may have a bad thermostat or some other problem.
Bob - 2003 Nissan Sentra SE-R SPEC V