Thermostat — Removal, Checking and Installation (BMW 3 Series E46)

Note: When installing the thermostat, the sealing ring and gasket must be replaced.

Removal

1. Disconnect the negative cable from the battery.

2. Drain the coolant as described in chapter 1.

Engine N42

3. Remove the wire clamp and disconnect the lower hose from the thermostat (Fig. 4.3). Disconnect the thermostat electrical connector (if there is one).



4. Remove the thermostat cover together with the thermostat itself by unscrewing the cover mounting screws (Fig. 4.4). The thermostat is made integral with the cover and only their assembly can be replaced. The sealing ring can be thrown away - a new one will be required during assembly.

M43TU engine and 6-cylinder engines

5. To access the thermostat, remove the cooling fan and viscous coupling as described in chapter 3.



6. Disconnect the hoses from the thermostat. On models with an electrically heated thermostat, disconnect the electrical connector plug from the thermostat.

7. Remove the thermostat housing by unscrewing the screws holding it in place (Fig. 4.7). Remove the gasket under the thermostat. On a 6-cylinder engine, to remove the thermostat housing, first remove the lifting eye from the cylinder head.



8. The thermostat is made integral with the body. Remove the sealing ring (Fig. 4.8).

Installation

9. Install the thermostat in the reverse order of removal, taking into account the following notes.

• a) Replace the thermostat sealing ring.
• b) Tighten the thermostat mounting screws to the specified torque.
• c) On models with a 6-cylinder engine, install a cooling fan.
• d) Finally, fill the cooling system.