Removal, installation and checking the thermostat (Opel Corsa C)

Caution: Do not open the expansion tank cap or remove the thermostat until the engine has cooled down completely! See also Section 2.

General information

1. The thermostat is designed to speed up the engine warm-up process and divides the cooling system into two circuits: large and small. Until the coolant temperature reaches a certain value (as a rule, thermostats are adjusted to a temperature of 80-90°C), the thermostat valve is closed and the liquid circulates along the small circuit without getting into the radiator. As a result, the engine quickly warms up to normal operating temperature. When a certain threshold value of the coolant temperature is exceeded, the thermostat filler begins to expand and opens the valve - the liquid begins to circulate along the large circuit through the radiator.

2. The thermostat housing is attached to the engine. The location of the thermostat may vary depending on the layout of the power unit, but it is easy to find - it is always connected to the upper radiator hose.

3. Below is a detailed description of the procedure for removing/installing the thermostat on Z10XE(P)/Z12XE/Z14XEP engines; for other engines, only the differences and features are given.

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Removal/installation

4. Disconnect the cable from the negative terminal of the battery (see Chapter 5). On Corsa-Eco models, remove the engine sump guard (see Chapter 2).



5. Drain the coolant (see Section 3).

Note: It is not necessary to drain the coolant completely. It is enough that the coolant level has dropped below the thermostat housing.

6. Loosen the clamp and remove the hose from the cooling system pipe (see accompanying illustration).



7. Unscrew 3 bolts and remove the thermostat housing together with the thermostat.

8. Installation is performed in the reverse order of removal. Replace the sealing gasket before installation (see accompanying illustration) and tighten the thermostat housing mounting bolts to the required torque.





9. Fill the system with coolant (see Section 3).

10. Start the engine, warm it up to operating temperature and check for leaks.

Features of Z14XE/Z16XE engines

10. Remove the engine cover (see Chapter 2).

11. Loosen the clamps and disconnect the throttle module preheating hose from the thermostat housing.

Features of the Z18XE engine

12. Remove the top engine cover (see Chapter 2).

13. Remove the bolt and release the air intake duct from the holder.

14. Disconnect the hose (see accompanying illustration) cooling system, disconnect the coolant temperature sensor wiring connector, remove the 2 mounting bolts and remove the thermostat housing from the engine.



15. Check the thermostat (see below), replace the thermostat if necessary. When replacing, do not forget to reinstall the coolant temperature sensor into the housing of the new thermostat, tighten it to the required torque (see Specifications).

Features of the Z16SE engine

16. Remove the timing belt, camshaft sprocket, tension roller and timing belt drive sprocket (see Chapter 2).



17. Disconnect the rear timing belt cover.

18. Unscrew the mounting bolts and remove the thermostat housing from the cylinder head (see accompanying illustration).



19. Remove the thermostat from its seat (see accompanying illustration).

Features of the Z13DT engine

20. On these models, the thermostat housing is installed under the vacuum pump and bolted to the cylinder heads.

Note: The thermostat cannot be removed from the housing - if necessary, it must be replaced together with the housing.

21. Remove the fuel filter and filter mounting clamp (see Chapter 4).

22. Unscrew 4 bolts and remove the air intake pipe.

23. Disconnect the sensor wiring connector (mounted on the thermostat housing) coolant temperature.



24. Loosen the mounting clamps and disconnect the 4 cooling system hoses from the thermostat housing.

25. Remove the thermostat housing mounting bolts (see accompanying illustration) and remove the housing.



26. Installation is performed in the reverse order of removal. When replacing the thermostat, move the temperature sensor from the old one to the new one.

Features of Y17DT(L)/ Z17DTH engines

27. Unscrew the mounting bolts and remove the thermostat housing cover (see accompanying illustration). Remove the thermostat.

Examination

28. The main reason for thermostat failure is the aging of the filler and its loss of ability to significantly change its volume depending on the temperature. Mechanical damage to the thermostat valve may also occur during operation.



29. You can first check the thermostat's functionality without removing it from the engine. With the engine running, open the hood and touch the upper radiator hose.

Warning: Be careful - high coolant temperatures can burn your hand!

If the engine has just started and has not yet reached operating temperature, and the liquid in the upper hose is already warm, then the thermostat valve is not closed. This is also indicated by a slower than usual increase in the coolant temperature, and in winter - a decrease in the heater power. If the control lamp has been activated (see Chapter "Controls and operating techniques") coolant temperature on the instrument panel, and the upper pipe is cold - it is guaranteed to say that the valve does not open the large circuit.

Note: This is only a rough check, and you must be sure that all other components of the cooling system and temperature control are functioning properly and that the coolant level is normal. Follow the recommendations given in the section on diagnosing cooling system problems (see Chapter "Introduction").

30. The most accurate results are obtained by checking the thermostat on a workbench.

31. Remove the thermostat from the engine (see above).

32. Tie a piece of wire to the thermostat assembly and lower it into a container filled with water (see accompanying illustration). Put the thermometer there too.

Attention: Make sure that the thermometer and thermostat do not come into contact with the walls and bottom of the container!

33. Begin to slowly heat the water, monitoring the change in the thermometer readings. The thermostat valve should operate in strict accordance with the control settings for a specific engine model (see Specifications).

34. Estimate the value of the full opening of the valve, - the nominal value is b - a = 8 mm (see accompanying illustration). If any deviations are detected, replace the thermostat.