Thermostat
1 - inlet pipe (from the engine); 2 - bypass valve; 3 - spring of the inlet valve; 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 - liquid outlet to the pump
At the thermostat, the main valve opening start temperature and the main valve stroke should be checked.
To do this, install the thermostat on the stand BS-106-000, lowering it into a tank with water or coolant. Place the bracket of the indicator leg into the main valve 9 from below. The initial temperature of the liquid in the tank should be 73–75°C. Increase the temperature of the liquid gradually by about 10°C per minute with gradual stirring so that it is the same throughout the volume of the liquid.
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 main valve opening start temperature is not within 81±54°C or the valve stroke is 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 tank 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.