To do this, install the thermostat on the stand, lowering it into a tank with water or coolant. Bottom to main valve 2 (pic. 2-66) support the indicator leg bracket.
Pic. 2-66. Thermostat:
1 - piston;
2 - main valve;
3 - solid thermosensitive filler;
4 - main valve spring;
5 - outlet pipe to the throttle pipe;
6 - bypass valve spring;
7 - bypass valve;
8 - inlet pipe from the engine;
9 - outlet pipe to the pump;
10 - rubber insert;
11 - piston holder;
12 - inlet pipe from the radiator;
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.
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.