1. Before finally being approved in opinion on a thermostat exit out of operation, check the level of cooling liquid in system, a state and effort of a tension of a driving belt (see the Head Nastroyki and routine maintenance), and also serviceability of functioning of the measuring instrument / a control lamp of temperature.
2. One of the possible reasons of too slow warming up of the engine (according to indications of the measuring instrument) is jamming of the thermostat in open situation. Replace the thermostat new.
3. In case of an overheat of the engine touch the lower hose of a radiator. If the hose is not heated, perhaps, the thermostat is jammed in a closed position, blocking circulation of cooling liquid through a radiator. Replace the thermostat.

Do not operate the car with the removed thermostat at all, - at the same time feedback of the onboard processor can be broken that will lead to increase in toxicity of the fulfilled gases and excessive increase in fuel consumption.

4. If the lower hose is heated, it means that cooling liquid regularly circulates through a radiator, i.e. the thermostat is open. Address materials of the Section devoted to diagnostics of malfunctions of the cooling system.
5. The most exact results are yielded by check of the thermostat on a workbench.
6. Remove the thermostat from the engine (see the Head Dvigatel).
7. Tie up a piece of a wire to assembly of the thermostat and lower it in the capacity filled with water. There lower the thermometer.

Track that the thermometer and the thermostat did not adjoin to walls and a bottom of capacity.

8. Begin to warm up slowly water, monitoring change of indications of the thermometer, - operation of the valve of the thermostat has to happen in strict accordance with requirements of Specifications.
9. Estimate the size of full opening of the valve, - the nominal rate makes 8 mm.
10. The description of procedures of removal and installation of the thermostat is provided in the Section Removal and installation of the thermostat.