1. Small circuit circulation (temperature up to +87°С) – the thermostat is closed. The bypass valve directs the coolant to the pump. From there, the liquid is again fed into the engine. This mode is used to quickly warm up the engine.
2. Mixed mode (temperature +87...+102°C) – the thermostat opens. The liquid, circulating along a small circuit, partially passes through the radiator.
3. Large circuit circulation (temperature over +102°C) – the thermostat is fully open. All liquid passes through the radiator.
Removing and checking the thermostat
If the thermostat gets stuck, it can cause major damage to the engine. The liquid will boil and evaporate quickly. In this case, you cannot continue driving. Have the vehicle towed to the repair site. Removing and installing the thermostat is a simple job. When purchasing a new thermostat, do not forget new gaskets, including the housing gasket. You will also need a container to drain the liquid. Remove the thermostat only when the engine is cold. Different models of thermostat housings have slightly different locations.
Sequence of work
1. Disconnect a wire from the negative plug of the storage battery.
2. Drain the coolant as described earlier.
3. Remove the front top engine cover.
4. Loosen the clamp, disconnect the radiator hose from the thermostat housing.
5. Disconnect the small expansion tank hose (after loosening the clamp).
Pic. 4.47. Thermostat location: 1 - thermostat housing; 2 - coolant pump; 3 - chain tensioner; 4 - exhaust manifold
Pic. 4.48. Coolant pump in block with thermostat: 1 - V-belt pulley flange; 2 - pump housing; 3 - pump impeller; 4 – the union of a hose of a radiator; 5 - thermostat housing; 6 - thermostat; A - from the radiator; B - from the engine; C - to the engine
6. Unscrew the thermostat housing and remove with it (pic. 4.47). Thermostat combined with water pump (pic. 4.48).
Pic. 4.49. Thermostat check
7. Place the thermostat in a container of water (pic. 4.49) and check the response temperature by slowly heating the water. For a thermostat that has already been in operation, a difference in the response temperature within±3°C is permissible.
8. Check that the valve closes completely when it cools down.
9. Replace thermostat if not working properly. On 4- and 6-cylinder engines, the thermostat has a one-piece design.
10. Before installing the thermostat, clean the gasket connections on the body and motor.
11. Establish the case with the thermostat and a new lining and wrap the moment of 10 Нм.
12. Connect the radiator hose, pay attention to its correct fit and secure tightening of the clamp.
13. Fill in coolant.
14. Connect a wire to the negative plug of the storage battery.
15. Warm up the engine and make sure that the bottom of the radiator heats up.
16. Check the tightness of the thermostat installation.