Cooling System Sensors and Switches — Checking, Removing and Installing (BMW 3 Series E46)

Thermal switch at the radiator outlet

Examination

1. Have the sensor checked by a BMW dealer.

Removal

2. The thermal switch is located in the lower radiator hose. Before removing the thermal switch, the engine and radiator must cool down.

3. Disconnect the negative cable from the battery.

4. Either partially drain the coolant to a level below the thermal switch, or prepare a plug that can be used to plug the hole while the thermal switch is out. If you choose to use a plug, be careful not to damage the radiator or bring any dirt into the radiator with the plug.

5. Disconnect the electrical wiring from the thermal switch (Fig. 7.5).



6. Release the temperature switch from the clamp and remove it from the radiator. Remove the sealing ring from it.

Installation

7. Install the sensor in the reverse order. Replace the sealing ring. Finally, fill the cooling system with liquid.

8. Start the engine and warm it up to operating temperature. Wait until the fan turns on and make sure that the cooling system maintains the desired temperature.

Coolant temperature sensor

Examination

9. Have the sensor checked by a BMW dealer.

Removal - N42 Engine

10. Either partially drain the coolant to a level below the sensor, or prepare a plug that can be used to plug the hole while it is away. If you choose to use a plug, be careful not to damage the hole for the sensor, and do not bring in any dirt with the plug.

11. The sensor is located on the left side of the cylinder block under the intake manifold (Fig. 7.11). To access the sensor, remove the generator (see 5A).



12. Disconnect the electrical connector from the sensor and unscrew the sensor from the cylinder block. Remove the sealing ring.

Removal - M43TU Engine and 6-Cylinder Engines

13. Either partially drain the coolant to a level below the sensor, or prepare a plug that can be used to plug the hole while it is away. If you choose to use a plug, be careful not to damage the hole for the sensor or bring any dirt into the cooling system with the plug.

14. The sensor is screwed into the left side of the cylinder head, under the intake manifold.

15. Disconnect the electrical wiring from the sensor. Unscrew the sensor from the cylinder head and remove the sealing washer (Fig. 7.15).

Installation

16. Place a new sealing washer on the sensor, screw the sensor into the cylinder head and tighten it securely.

17. Connect the electrical wiring to the sensor. Fill the cooling system.