my BMW 3 Series F30/F31 (2012-2019) temperature gauge fluctuates what's wrong

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent electrical shorts during the repair.
• Allow the engine to cool completely before proceeding.

2. Inspect and Replace Temperature Sensor

• Tools Required: Socket set, multimeter, coolant catch pan, new temperature sensor.
• Remove the connector from the temperature sensor.
• Use a socket to unscrew the old temperature sensor from the engine block.
• Install the new temperature sensor and torque it to the manufacturer's specifications (typically around 15-20 Nm).
• Reconnect the sensor's electrical connector.

3. Thermostat Inspection and Replacement

• Tools Required: Socket set, gasket scraper, new thermostat, thermostat gasket.
• Drain the coolant into a catch pan.
• Remove the thermostat housing bolts with a socket set.
• Take out the old thermostat and inspect for proper operation (it should open and close smoothly).
• Clean the mating surfaces with a gasket scraper.
• Install the new thermostat and gasket, then reattach the thermostat housing.
• Refill the cooling system with the appropriate coolant mixture.

4. Test Cooling System

• Tools Required: Coolant pressure tester (optional).
• Reconnect the battery.
• Start the engine and allow it to reach operating temperature.
• Monitor the temperature gauge for stability.
• Check for leaks around the thermostat housing and temperature sensor.