Thermostat — Removal, Checking and Installation (Audi 100 C3)

1. On four-cylinder engines, the thermostat is located at the base of the water pump housing; on five-cylinder engines, it is located behind the water pump on the left side of the cylinder block.

2. Before removing the thermostat, first drain the cooling system as described in Chapter 3.

3. Unscrew and remove the thermostat cover, remove the O-ring (photo).







4. Remove the thermostat from the casing (photo).





5. To test the thermostat, lower it by a string into a container of water. Gradually heat the water and note the temperatures at which the thermostat begins to open and opens completely. Remove the thermostat from the water and check that it closes completely after cooling. Replace the thermostat if its parameters differ from the information given in Specifications.

6. Clean the thermostat housing and mating surfaces, install a new O-ring on the cover (four cylinder engines). On five-cylinder engines, place a new O-ring on the thermostat and insert the thermostat into the housing (photo).



7. Install the thermostat and tighten the bolts evenly.

8. Fill the cooling system as described in Chapter 5.