Thermostat - removal, testing and refitting
Removal
1 Drain the cooling system.
2 Loosen the retaining clips and detach the degas and radiator top hoses from the thermostat housing. On the CVH engine, also detach the heater hoses.
3 Disconnect the lead from the thermal switch on the thermostat housing.
Disconnect the fan thermal switch lead - OHV
4 Unscrew and remove the retaining bolts, then lift clear the thermostat housing.
Thermostat housing and retaining bolts - CVH
5 Prise free and lift out the thermostat, noting its orientation. On the CVH engine, detach the circlip to allow the thermostat to be removed together with its O-ring.
Thermostat retaining clip - CVH
Remove the thermostat . . .
. . . and seal ring - CVH
Testing
6 To test the thermostat, first check that in a cold condition its valve plate is closed. Suspend it in a pan of water and gradually heat the water.
Thermostat checking method
At, or near boiling, the valve plate should be fully open. A more accurate
assessment of the opening and closing points of the thermostat can be made if a
thermometer is placed in the water and results compared with the temperatures
given in the Specifications. Check that the thermostat closes again as the water
cools down.
Refitting
7 Refitting is a reversal of removal. Always use a new gasket and apply a little jointing compound to the threads of the thermostat housing bolts before screwing them in. Use new hoses and clips where necessary.
Thermostat refitted (CVH) with new hoses and clips