Coolant level sensor
Removal
Location of the coolant level sensor on the expansion tank
1. The sensor is installed on the side wall of the expansion tank (see picture). Remove the sensor on a cold engine. Partially drain the coolant so that the expansion tank is empty.
2. Disconnect the electrical connectors from the coolant level sensor.
3. Remove the retaining ring and remove the coolant level sensor from the expansion tank. Remove the sealing ring.
4. Connect an ohmmeter to the sensor contacts and measure the sensor resistance.
5. If the sensor float is set to the upper position, the sensor contacts should be open. When the float is set to the lower position, the sensor contacts should be closed.
Installation
1. Installation is performed in the reverse order of removal. Install a new sealing ring on the sensor body. Fill the cooling system with coolant.
Coolant Temperature Gauge Sensor
The coolant temperature gauge sensor is screwed into the upper left side of the cylinder head. Do not confuse it with the engine management system coolant temperature sensor, which is located nearby.
Removal
1. Remove the sensor on a cold engine. Partially drain the coolant from the cooling system.
2. Disconnect the electrical connector from the sensor, unscrew the sensor from the cylinder head and remove the sealing ring.
Installation
1. Installation is performed in the reverse order of removal. Install a new sealing ring on the sensor. Add coolant to the cooling system.
Information copied from the website (mercedesman.ru)