Thermostat
1 – inlet pipe (from the engine); 2 – bypass valve; 3 – pre-release 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 – radiator inlet pipe; 14 – filler; 15 – clip; D – fluid inlet from engine; P – liquid inlet from radiator; H – liquid outlet to the pump
The thermostat should be checked for the temperature at which the main valve starts to open and for the stroke of the main valve.
To do this, install the thermostat on the BS-106-000 stand, lowering it into a tank with water or cooling liquid. From below, rest the indicator leg bracket against the main valve 9. The initial temperature of the liquid in the tank should be 73–75°C. Gradually increase the temperature of the liquid by about 10°C per minute with gradual stirring so that it is the same throughout the entire volume of liquid.
The temperature at which the main valve stroke is 0.1 mm is taken as the temperature at which the valve starts to open.
The thermostat must be replaced if the main valve opening temperature is not within 81±54°C or the valve stroke is less than 6.0 mm.
The simplest check of the thermostat can be done by touch directly on the car.
After starting a cold engine with a working thermostat, the lower radiator tank should heat up when the liquid temperature gauge needle is approximately 3–4 mm from the red zone of the scale, which corresponds to 80–85°C.