Nissan sentra n16 temp. overheating

Usual over heating issues lead to waterpump failure-when running the motor- pop the hood to listen for what sound like marbles or bearings rolling around on the side of the block, also if you see coolant leaking out of the weep holes- your water pump has failed. Other trouble shooting you can do is check the thermostat to see if it opens at the correct temp- i remember a couple years ago i had thought my thermostat was faulty so what i did is I placed it in pan of water with a thermometer, as i gradually increased water temp thermostat opened like it should. So that eliminated that possible cause. Also check for coolant temp sensor or possible coolant leaks along the seams of the OEM radiator. The OEM radiator came with plastic end tanks- i should know- mine had a coolant leak appear just at the top near the radiator cap. Drove me crazy until i cleaned my entire motor and ran the motor and sure enough- the little green leak started appearing right there at the seam. Replaced it with a OEM new one (or go with a Koyo if you can find one cheap)with aluminum welded end tanks(no plastic to crack) and no more problems- mine has been leak free ever since. Also check to make sure fans are wired properly. Go by process of elimination-sometimes your expensive leak could be solved cheaper.

For more troubleshooting check the link below:

http://www.allcarhelp.com/2016/05/1994-nissan-sentra-overheat.html

Verify the sending unit is correct. Verify it is overheating. Sometimes the sending unit and/or gauge is bad.

Did they replace the thermostat? If so check to make sure that nothing is plugging the radiator or heater core?

Maybe your radiator is clogged.

you could have an air lock would bleed heater hoses

Are you sure there is not a air pocket in the engine after changing water pump,
there is only 1 thermostat

you've got a possible blockage in the head or block.

I have 2002 Nissan ser with 120k, and I noticed a different temperature change when I start my car up...it takes a while to get warm. The weather has been cold lately, but my car has quick jolt as I'm driving until the car warms up. What is this issues I'm having...?????

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

most likely a thermostat because the pressure on the a\c will be high if engine is over heating or the fans are not kicking on (check fan relay)