Thermostat — General Information (Mercedes-Benz S-Class W116)

The thermostat is located in the housing on the cylinder head. A ball valve in the thermostat ensures automatic removal of air from the cooling system when filling with coolant.

To remove the thermostat, remove the hose from the housing cover, unscrew the cover mounting bolts and remove it. Remove and check the condition of the sealing ring.

The thermostat cannot be repaired and must be replaced if damaged. Simple tests can be performed to check its functionality:

Place the thermostat on a piece of wire into a container with cold water and secure it.

Secure the thermometer in the same way.

Heat the water in the container and note the temperature at which the thermostat begins to open, it should be within 87°C. At 105°C the thermostat should be fully open.

Original published on the website MercedesMAN

During these tests the pin should move by 6...8 mm. If the thermostat does not pass the test, it must be replaced.

When installing the thermostat, install a new gasket. Check the hose clamp. Fill the cooling system with coolant (section 5.1.1).