Note: Refer to the warnings given in Section 1 of this Chapter before proceeding.

Removal
1 The thermostat housing is located on the cylinder head adjacent to the distributor.

2 Drain the cooling system as described in Chapter 1.

3 Disconnect the radiator top hose from the thermostat housing. Where necessary for access, also remove the air inlet duct from the air cleaner.

4 Unscrew and remove the two thermostat housing cover bolts and remove the cover.

This may need a little persuasion with a wooden or plastic-faced hammer (see illustration).

4.4 Removing the thermostat housing cover on XV, XW and XY series engines

5 Remove the thermostat. If it is stuck, do not lever it out under its bridge piece, but cut around its edge with a sharp knife.

6 Remove the rubber ring(s) and clean the mating faces of the housing and cover.

Testing
7 If the thermostat is suspected of being faulty, suspend it in a container of water which is being heated. Using a thermometer, check that the thermostat starts to open at the specified temperature and is fully open also at the specified temperature.

8 Remove the thermostat from the water and allow it to cool. The valve plate should close smoothly.

9 If the unit fails to operate as described or is stuck open or shut, renew it with one of similar temperature rating (see illustration).

4.9 Thermostat temperature rating (arrowed) stamped on base

Refitting
10 Refitting is a reversal of removal but use new rubber sealing ring(s). Refill the cooling system as described in Chapter 1 on completion.