The need to replace the thermostat may arise when the engine temperature is unstable: overheating or insufficient warming up.
To check the thermostat on a car, start a cold engine and touch the upper radiator hose with your hand - it should be cold. After the coolant temperature reaches (105±1.5)°C, the hose should quickly heat up, which indicates that the liquid has started to circulate through the large circuit. If this does not happen, remove the thermostat and check its functionality.
1. Disconnect the wire from the negative terminal of the battery.
2. Drain the fluid from the engine cooling system (see "Replacing the coolant").
3. Squeeze the locking clip of the thermostat heating element wire harness connector...
4. ...and disconnect the connector.
5. Loosen the clamp securing the radiator supply hose by squeezing its bent ears with pliers, slide the clamp along the hose...
6. ...and disconnect the hose from the thermostat pipe.
7. Remove the four bolts securing the thermostat to the water distributor...
8. ...and remove the thermostat.
9. Install the thermostat in the reverse order of removal.
NOTE: Check the condition of the thermostat sealing ring. If it is too tight or torn, replace it with a new one.
10. Fill with coolant (see "Replacing the coolant").