Check without removing the thermostat
1. Before removing and testing the thermostat, make sure that engine cooling problems are not due to insufficient coolant or loose drive belt tension. Make sure the indicator located on the instrument cluster is working.
2. If the engine warms up to operating temperature for a long time (according to the indicator), the thermostat may be stuck open. In this case, the thermostat must be replaced.
3. On the other hand, a long warm-up may be due to the lack of a thermostat. This could have been done on purpose or unintentionally (forgot to install after repair). Do not drive the car without a thermostat. The engine management system will maintain the warm-up mode of the unit for longer, in which the engine consumes more fuel, and the exhaust gases contain a greater amount of harmful impurities.
4. If the engine overheats, feel the upper radiator hose. If it's not hot and the engine is overheated, the thermostat may be stuck in the closed position. The liquid 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 liquid circulates normally through the system - read the recommendations given in Section Troubleshooting.
Test with thermostat removal
Check of serviceability of functioning of the thermostat
1 - Thermostat
2 - poppet valve
1. Remove the thermostat (see Section Removal and installation of the thermostat).
2. If the thermostat is open at room temperature, it is defective and must be replaced.
3. For a rough test of the thermostat's performance, hang it on a piece of twine in a container of water. The thermostat must not touch the walls of the container. Start heating the container.
Note. From the moment the temperature reaches a value of 8°C below the point where the valve starts to open, the heating rate should not exceed 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 until the valve closes completely.
5. If the thermostat does not open when heated or does not close when cooled, replace it.
6. When installing the thermostat, pay attention to the following points:
- Make sure that the mating surfaces are thoroughly cleaned, do not forget to prepare and install a new sealing ring;
- Track correct orientation of the thermostat in a casing;
- Make sure the cover bolts are tightened to the correct torque (see Specifications);
- Refueling the cooling system (see chapter Ongoing care and maintenance) start only after making sure that all hoses are connected correctly;
- After installation is complete, start the engine, warm it up to normal operating temperature, and check for signs of leaks.