To do this, install the thermostat on the stand BS-106-000, lowering it into a tank with water or coolant. From the bottom to the main valve 9 (pic. 2-66) support the indicator leg bracket.
Pic. 2-66. Thermostat:
1 - inlet pipe (from the engine); 2 - bypass valve; 3 - bypass valve spring; 4 - glass; 5 - rubber insert; 6 - outlet pipe; 7 - main valve spring; 8 - main valve seat; 9 - main valve; 10 - holder; 11 - adjusting nut; 12 - piston; 13 - inlet pipe from the radiator; 14 - filler; 15 - clip; D - fluid inlet from the engine; P - fluid inlet from the radiator; H - fluid outlet to the pump.
The initial temperature of the liquid in the tank should be 73-75°C. Increase the temperature of the liquid gradually by about 1°C per minute with constant stirring, so that it is the same throughout the volume.
The temperature at which the main valve stroke is 0.1 mm is taken as the temperature at which the valve opens.
The thermostat must be replaced if the start temperature of the main valve is not within (80±2) °C or main valve stroke less than 6.0 mm. For thermostats made in Poland, the main valve opening start temperature is (83±2) °C.
The simplest thermostat test can be carried out by touch directly on the car. After starting a cold engine with a working thermostat, the lower radiator pipe should heat up when the needle of the fluid temperature gauge is approximately 3-4 mm from the red zone of the scale, which corresponds to 80-85°C.