my BMW 3 Series F30/F31 (2012-2019) has a coolant temperature warning

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery before starting any electrical repairs.

2. Inspect and Replace Coolant

• Tools Required: Radiator cap tool, funnel
• Sub-steps:
  1. Remove the radiator cap carefully to avoid pressure release.
  2. Inspect the coolant for contamination; replace if dirty or low.
  3. Refill the coolant to the recommended level, using a mixture of BMW-approved coolant and distilled water.

3. Replace Coolant Temperature Sensor

• Tools Required: Socket set, torque wrench
• Sub-steps:
  1. Locate the coolant temperature sensor, typically found near the thermostat housing.
  2. Disconnect the electrical connector from the sensor.
  3. Use a socket to remove the old sensor and install the new one.
  4. Torque the new sensor to the manufacturer's specifications (check the service manual).
  5. Reconnect the electrical connector.

4. Replace Thermostat (if faulty)

• Tools Required: Socket set, gasket scraper, torque wrench
• Sub-steps:
  1. Drain the coolant from the system.
  2. Remove any hoses connected to the thermostat housing.
  3. Unbolt the thermostat housing and remove the old thermostat.
  4. Clean the mating surfaces of the housing and engine.
  5. Install the new thermostat and gasket, ensuring correct orientation.
  6. Reattach the thermostat housing and hoses, then torque bolts as specified.

5. Check Radiator and Fan Functionality

• Tools Required: Multimeter, coolant pressure tester
• Sub-steps:
  1. Inspect the radiator for blockages and clean if necessary.
  2. Check the operation of the radiator fan by connecting it directly to the battery to ensure it spins.
  3. If the fan does not operate, replace the fan assembly as needed.
  4. Use a coolant pressure tester to check for leaks in the system.