Thermostat

Withdrawal

Remove the negative terminal from the battery. Drain the coolant from the cooling system.

Engines and HCS, Endura-E, CVH and PTE

Loosen the clamps and remove the hoses of the upper tank of the radiator, expansion tank and heater from the thermostat housing (see fig. 3.3, 3.4).





Remove the connector from the temperature sensor for turning on the fan Unscrew the bolts and remove the thermostat housing (see figure 3.5.).



Remove the gasket from the front surface of the thermostat housing, then using pliers, squeeze and remove the retaining ring from the thermostat housing. Remove the thermostat from the housing and remove the O-ring (see fig. 3.6-3.8).








Zetec and Zetec-E engines.
Remove the expansion tank and radiator top tank hoses from the thermostat housing.

Unscrew the mounting bolts and remove the water outlet pipe from the thermostat housing (see fig. 3.9).



Remove the thermostat from the housing, marking its position.

General control of the cooling system

If there are defects in the cooling system, check the coolant level, the tension of the auxiliary drive belt and the operation of the temperature gauge.

If after starting the engine warms up very slowly, then the thermostat may be in a permanently open position and it needs to be replaced.

If the engine overheats, check the temperature of the upper radiator hose by hand. If the hose is cold, then the thermostat may be in the closed position and not letting coolant through to the radiator. In this case, the thermostat must also be replaced.

Thermostat check

If the thermostat is in the open position at room temperature, it must be replaced.

To test the thermostat, lower it with twine into a container of water. Gradually heating the water, measure the temperature at which the thermostat begins to open and fully opens. Remove the thermostat from the water and check that it closes completely after it cools down. Replace the thermostat if it is out of specification (see figure 3.10).

Installation (all models)

Installation is made in sequence, return to removal. Clean mating surfaces and replace thermostat o-ring and housing gasket (see fig. 3.11).




On Zetec and Zetec-E engines, install the thermostat with the valve on top (see fig. 3.12).



Tighten the thermostat housing bolts to the required torque. Fill the cooling system with coolant. Start and warm up the engine to operating temperature. Check the cooling system for leaks and thermostat operation.