A failing coolant temp sensor can manifest a variety of problems. Sometimes it can give you a faulty reading on the temp gauge on the instrument panel. Other times, it can prevent the cooling fans mounted on the radiator from operating correctly. These problems can be a bit troublesome to diagnose. I recommend scanning the vehicle with the factory VADIS software or aftermarket software to search for any fault codes that may be stored.
You'll want to drain off some of the coolant in the system before you remove the sensor. If you fail to do so, you'll get coolant streaming out of the mounting hole. You just need to remove enough coolant so that the level is below the height of the sensor location. See our article on Coolant Change for information. Don't forget to bleed the cooling system of air after replacing the sensor.
Youll also need to remove the air filter housing to access the sender. See our article on Air Filter Housing Removal for more information.
Shown here is the coolant temp sender (green arrow) mounted in the thermostat housing. Press the tab on the electrical connector (yellow arrow) and pull it off the temp sender.