Checking the Thermostat (VAZ-2105)

Check the start of opening and the stroke of the main valve of the thermostat. To do this, fix it on the BS-106-000 thermostat test stand and lower it into water, the temperature of which should be 73-75°C, i.e. 5-7°C lower than the opening temperature of the main valve. Rest the indicator leg bracket against the main valve.

Gradually increase the water temperature by approximately 1°C per minute while stirring constantly. The temperature at which the main valve stroke is 0.1 mm is taken as the temperature at which the main valve begins to open. If the temperature at which the main valve begins to open is not within the range of 77–86°C or the valve stroke is less than 6 mm, replace the thermostat with a new one.

The thermostat's serviceability can also be checked directly on the car. If the thermostat is in good condition, the radiator outlet pipe should heat up after starting a cold engine when the fluid temperature reaches 80-85°C, and the fluid temperature indicator arrow should be approximately 3-4 mm from the red zone of the scale.

(The text is copied from the online resource VAZbook.ru)