Where is the coolant temperature sensor located on 2000 Altima?

Watch the temp gauge when the electric radiator fans come on. The temp sensor that controls when the fan comes on may be faulty.

Any chance of a head gasket leak? Is the coolant level still full? These were known for head gasket issues. Coolant is a closed system and level will not drop unless there is a leak. Make sure there is no air in the system. Replace the radiator cap to make sure that it is operating properly.

if your fans are electric check fuses and relay if they are good replace your coolant temp sensor that is what is most likely wrong anyway cheap at auto zone they are normally located right by thermostat housing or in the side of the block it tells your cars ecu when to cut on fans.

if your fan is belt driven replace you fan clutch and problem solved


if this helps you could you leave me good feedback thanks

It certainly could be the sensor and it is mostly cheaper and easier to replace it as a first step.

Bear in mind the temperature gauge can only be reasonably accurate if it is supplied by the correct stabilised voltage and sometimes the instrument voltage stabiliser does cause problems...

YOU NEED BLEED COOLANT SYSTEM.CHECK COOLANT LEVEL IN RADIATOR.ADD MORE DEXCOOL UNTIL COOLANT LEVEL IS CLOSE TO RADIATOR SPOUT.CRANK ENGINE LET IDLE UNTIL TOP RADIATOR HOSE GET HOT.WATCH TEMPERATURE GAUGE.IF TEMPERATURE GAUGE START RISING TO HOT ZONE.TURN OFF ENGINE.LET COOL DOWN.USE LARGE RAG SLOWLY OPEN RADIATOR CAP A LITTLE AT A TIME UNTIL ALL PRESSURE RELIEVED.REMOVE RADIATOR CAP.ADD MORE COOLANT.CRANK CAR AGAIN LET IDLE UNTIL TOP RADIATOR GET HOT.KEEP EYE ON TEMP.GAUGE ALSO.WHEN TEMP.GAUGE STOP CLIMBING.YOUR COOLANT SYSTEM BLED.WHEN DONE LET CAR SET A WHILE CHECK COOLANT LEVEL.ALSO FIRST THING IN THE MORNING CHECK COOLANT LEVEL AGAIN.AND BESURE ADD COOLANT IN THE OVERFLOW JUG TO THE COLD MARK.DONT OVER FILL THE COOLANT RESERVOIR JUG.WORK SAFELY DONT GET SCALDED.

Locate the temp switch in the engine bay, if its a single wire just earth it and see if your gauge moves. If it does then get a new switch.

There is a coolant temperature sensor on the top engine block to measure the temperature. Either the connector is loosen or the temp sensor is bad. This sensor is bad will cause the gauge reading fluctuated. Locate the temp sensor and replace it to take care of the problem.

I have seen this happen to a few cars when they were running REALLY low on coolant (anti-freeze) AND/OR had a major air pocket trapped in the cooling system.
Heres whats going on:
The gauge is driven by a temperature sensor that sticks into the cooling system. When your really low on coolant, some times the temperature sensor is exposed to air, instead of liquid coolant and the temperature of the sensor drops. As your driving around sometimes liquid coolant touches the sensor and the temperature reading will spike again to normal readings or to an even hotter reading then normal (because what little fluid is in the system is not enough to maintain proper temps).
If you recently filled up or topped off the coolant from a low coolant situation then you may have a major air bubble locked in the system, although this is far less likely in the small Sentra cooling system, but you never know.
Lastly, the sensor itself or the plug into the sensor is loose, broken, or shorting. You or someone you know can try to locate the coolant sensor for the gauge and see if the connect to the sensor is loose or the wire have become damaged, giving you readings all over the place.
nissanhelp . com is a great place for help and you can find factory service books on there. You can join for free and ask questions.

The problem is almost for sure the guage, replace it.