Peugeot 405 Manual

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


Removal
Note: A new sealing ring may be required on refitting.

1 Disconnect the battery negative lead.

2 Drain the cooling system as described in Chapter 1.

3 Where necessary, release any relevant wiring and hoses from the retaining clips, and position clear of the thermostat housing to improve access. On some models, access is also improved if the air cleaner ducting is removed is removed (see Chapter 4).

4 Unscrew the retaining bolts, and carefully withdraw the thermostat housing cover to expose the thermostat. Take care not to strain the coolant hose(s) connected to the cover (see illustrations).

4.4a Thermostat housing cover retaining bolts (arrowed) - 1.4 litre engine
4.4a Thermostat housing cover retaining bolts (arrowed) - 1.4 litre engine

4.4b Thermostat housing cover (arrowed) - 2.0 litre engine
4.4b Thermostat housing cover (arrowed) - 2.0 litre engine

5 Lift the thermostat from the housing, and recover the sealing ring(s) (see illustration).

4.5 Removing the sealing ring from the thermostat flange
4.5 Removing the sealing ring from the thermostat flange

Testing
6 A rough test of the thermostat may be made by suspending it with a piece of string in a container full of water. Heat the water to bring it to the boil - the thermostat must open by the time the water boils. If not, renew it.

7 If a thermometer is available, the precise opening temperature of the thermostat may be determined; compare with the figures given in the Specifications. The opening temperature is also marked on the thermostat.

8 A thermostat which fails to close as the water cools must also be renewed.

Refitting
9 Refitting is a reversal of removal, bearing in mind the following points: a) Examine the sealing ring(s) for signs of damage or deterioration, and if necessary, renew.

b) Ensure that the thermostat is fitted the correct way round, with the spring(s) facing into the housing.

c) On completion, refill the cooling system as described in Chapter 1.


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