Warning! Do not open the radiator cap or remove the thermostat until the engine has cooled down completely! See also the warning at the beginning of the Section Antifreeze - general information.
Examination
1. Before you finally decide that the thermostat is out of order, check the coolant level in the system, the condition and tension of the drive belt (see Chapter Settings and ongoing maintenance), as well as the proper functioning of the temperature gauge/control lamp.
2. One possible reason for the engine warming up too slowly (according to the meter readings) is that the thermostat is stuck in the open position. Replace the thermostat with a new one.
3. If the engine overheats, feel the lower radiator hose with your hand. If the hose is not hot, the thermostat may be stuck in the closed position, blocking the circulation of coolant through the radiator. Replace the thermostat.
Attention! Never operate the vehicle with the thermostat removed, as this may disrupt the feedback of the on-board processor, which will lead to increased toxicity of exhaust gases and excessive increase in fuel consumption.
4. If the lower hose is hot, this means that the coolant is circulating properly through the radiator, i.e. the thermostat is open. Refer to the materials in the Section on diagnosing faults in the cooling system.
5. The most accurate results are obtained by checking the thermostat on a workbench.
6. Remove the thermostat from the engine (see Chapter Engine).
7. Tie a piece of wire to the thermostat assembly and lower it into a container filled with water. Lower the thermometer there as well.
Attention! Make sure that the thermometer and thermostat do not come into contact with the walls and bottom of the container.
8. Start heating the water slowly, monitoring the change in the thermometer readings - the thermostat valve should operate in strict accordance with the requirements Specifications.
9. Estimate the value of the full opening of the valve - the nominal value is 8 mm.
10. A description of the procedures for removing and installing the thermostat is given in Section Removal and installation the thermostat.