Checking without removing the thermostat
1. Before removing and checking the thermostat, make sure that the engine cooling problems are not due to insufficient coolant or poor drive belt tension. Make sure the indicator on the instrument cluster is working properly.
2. If the engine takes a long time to warm up to operating temperature (according to the indicator readings), the thermostat may be stuck open. In this case, the thermostat should be replaced.
3. On the other hand, a long warm-up may be due to the absence of a thermostat. This could have been done intentionally or unintentionally (forgot to install after repair). Do not use the car without a thermostat. The engine management system will maintain the warm-up mode of the unit longer, in which the engine consumes more fuel, and the exhaust gases contain more harmful impurities.
4. If the engine is overheating, feel the upper radiator hose. If it is not hot and the engine is overheating, the thermostat may be stuck in the closed position. Fluid does not enter the radiator and circulates in a small circle. In this case, replace the thermostat.
5. If the upper radiator hose is hot, this means that the thermostat is open and the fluid is circulating normally in the system - read the recommendations given in Section Troubleshooting.
Checking with thermostat removal
Checking the proper functioning of the thermostat
1 - Thermostat
2 - Plate valve
1. Remove the thermostat (see Section Removal and installation the thermostat).
2. If the thermostat is open at room temperature, it is faulty and must be replaced.
3. To roughly check the thermostat's functionality, hang it on a piece of string in a container of water. The thermostat should not touch the walls of the container. Start heating the container.
Note: Once the temperature reaches 8°C below the valve opening point, the heating rate should be no more than 1-2°C/min.
4. As the water heats up, the thermostat should open (this happens just before the water boils). Since the boiling point of water is 100°C, the thermostat may not open fully (see Specifications). Remove the thermostat and let it cool down - the valve should close completely.
5. If the thermostat does not open when heating or does not close when cooling, replace it.
6. When installing the thermostat, pay attention to the following points:
- Make sure the mating surfaces are thoroughly cleaned, do not forget to prepare and install a new sealing ring;
- Make sure the thermostat is oriented correctly in the housing;
- Make sure that the cover mounting bolts are tightened to the required torque (see Specifications);
- Filling the cooling system (see Chapter Routine care and maintenance) start only after making sure that all hoses are connected correctly;
- Once installation is complete, start the engine, warm it up to normal operating temperature and check for signs of developing leaks.
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