Thermostat - removal, testing and refitting

Cooling, heating and ventilation systems / Thermostat - removal, testing and refitting

Removal
1 The thermostat is located in the outlet housing on the left-hand end of the cylinder head. To remove it, first drain the cooling system as described in Chapter 1.

2 Unscrew the bolts and remove the thermostat cover (see illustrations). Place the cover with top hose still attached to one side.

4.2a Unscrew the socket head bolts. . .

4.2b . . . and remove the thermostat cover

3 Remove the sealing ring (see illustration).

4.3 Removing the thermostat cover sealing ring

4 Extract the thermostat from the outlet housing.

Testing
5 To test whether the unit is serviceable, suspend it with a piece of string in a container of water. Gradually heat the water and note the temperature at which the thermostat starts to open. Continue heating the water to the specified fully open temperature then check that the thermostat has opened by at least the minimum amount given in the Specifications.

Remove the thermostat from the water and check that it is fully closed when cold.

6 Renew the thermostat if it fails to operate correctly.

7 Clean the thermostat seating and the mating faces of the outlet housing and cover.

Refitting
8 Refitting is a reversal of removal, but fit a new sealing ring and tighten the cover bolts to the specified torque. Fill the cooling system as described in Chapter 1.