Inlet manifold preheating - testing

Fuel and exhaust systems - carburettor models / Inlet manifold preheating - testing

Heater element
1 The inlet manifold is preheated by coolant from the cooling system and by a heater element located in the bottom of the inlet manifold.

2 To check the heater element, the engine should be cold. Disconnect the wire from the element at its in-line connector, then attach an ohmmeter between the wire connector from the element and earth. This should record 0.25 to 0.50 ohm.

3 To remove the element, disconnect the wire then unscrew the bolts and withdraw the unit.

Remove the sealing ring and gasket (see illustrations). When refitting, always renew the sealing ring and gasket.

18.3a Unscrew the bolts . . .

18.3b . . . and remove heater element from inlet manifold

18.3c Removing sealing ring from heater element

Thermo-switch
4 On 1.05 and 1.3 litre engines, the heater element is controlled by a thermo-switch located in the coolant supply hose to the inlet manifold. On 1.6 and 1.8 litre engines, the thermo-switch is located in the top of the coolant hose connecting piece mounted on the side of the cylinder head.

5 Before removing the thermo-switch, drain off some engine coolant to reduce spillage when the switch is removed.

6 To test the thermo-switch, first detach the lead connector. Unscrew and remove the switch from the housing and plug the hole to stop any leakage of coolant.

7 With an ohmmeter connected to the terminals, gradually heat the base of the switch unit in hot water. Below the following temperatures there should be zero resistance (ie. internal contacts closed): 1.05 litre engine - 65°C 1.3, 1.6 and 1.8 litre engines - 55°C 8 Above the following temperatures there should be a maximum resistance (ie. internal contacts open):
1.05 litre engine - 75°C 1.3, 1.6 an d 1.8 litre engines - 65°C 9 If defective, the switch must be renewed.