Coolant Temperature Sensor/Switch (For Computer): Service and Repair

Replacing the engine coolant temperature (ECT) sensor

Removing the temperature sensor
Remove the cap from the expansion tank.
Raise the car. Remove the lower splashguard.
Position a container under the engine drain cock. Drain the engine coolant.
Close the cock.
Install the lower splash guard.
Lower the car.




Remove the screw holding the engine stabilizer brace to the bracket on the engine.
Undo the clamp holding the return hose for the power steering.
Remove the cross stay.





Applies only to B6xx4T
Remove the crankcase ventilation pipe from the intake manifold. Start with the cover.
Remove the plastic hoses between the turbocharger (TC) and the charge air cooler and between the air cleaner (ACL) and the turbocharger (TC).
Remove the clamp for the intake manifold at the turbocharger (TC) for cylinders 1, 2 and 3. Turn the upper section of the pipe towards the firewall.





Remove
- the upper timing belt cover.
Lift up the servo reservoir and place it on top of the engine

Warning! Seal the cover for the servo reservoir. Check that no oil leaks out. Servo oil is highly inflammable.

- the screw for the front timing belt cover
Applies only to B6xx4T engines. For cars with chassis numbers203779-, see Timing cover front, replacing Service and Repair
- the timing belt cover.
Disconnect the connector for the sensor cable.
Remove the variable valve timing solenoids and place them to one side.
Remove the screw for the cable duct.




Remove the thermostat housing with the cable duct.
Clean the mating surfaces of the cylinder block. Ensure that no dirt enters the fluid ducts.




Secure the thermostat housing in a vise. Remove the sensor.

Note! Handle the thermostat housing carefully when securing it in the vise.

Installing the temperature sensor
Clean the thermostat housing mating surfaces. Ensure that there is no dirt left in the thermostat housing.

Install
- the new sensor. Use anew gasket. Tighten to 20 Nm. Ensure that the sensor cable is correctly routed in the thermostat housing and in the cable duct
- the thermostat housing using a new gasket. Tighten to 17 Nm
- the screw for the cable duct. Tighten to 10 Nm
- the variable valve timing solenoids. Tighten to 10 Nm
- the front timing belt cover.Applies only to B6xx4T engines. For cars with chassis numbers203779-, see Timing cover front, replacing Service and Repair. The mudguard over the right drive shaft boot may come loose. If this happens, secure it from underneath
- the screw for the front timing belt cover. Tighten to 12 Nm
- the servo reservoir. Check that the hoses are correctly positioned
- the upper timing belt cover.

Applies only to B6xx4T
Install the plastic hoses between the turbocharger (TC) and the charge air cooler and between the air cleaner (ACL) and the turbocharger (TC).
Install the crankcase ventilation pipe on the intake manifold.
Tighten all hose clamps.

Install
- the engine stabilizer brace. Tighten to 50 Nm
- the torque rod on the bracket on the engine. Tighten to 80 Nm
- the clamp holding the return hose for the power steering.

Function test
Fill with coolant.
Install the cap on the expansion tank.
Test drive the engine until the thermostat has opened.
Top up the coolant if necessary.