At the thermostat it is necessary to check temperature of the beginning of opening of the main valve and the course of the main valve.

Fig. 3-66. Thermostat: 1 — an entrance branch pipe (from the engine); 2 — perepuskny the valve; 3 — a spring of the perepuskny valve; 4 — a glass; 5 — a rubber insert; 6 — an output branch pipe; 7 — a spring of the main valve; 8 — a saddle of the main valve; 9 — the main valve; 10 — the holder; 11 — an adjusting nut; 12 — the piston; 13 — an entrance branch pipe from a radiator; 14 — a filler; 15 — a holder; Д — a liquid input from the engine; Р — a liquid input from a radiator; N — a liquid exit to the pump

For this purpose install the thermostat at the BS-106.000 stand, having lowered in a tank with water or cooling liquid. From below rest an indicator leg arm against the main valve 9 (fig. 3-66).

Reference temperature of liquid in a tank has to be 73–75 °C. Gradually increase liquid temperature approximately by 1 °C a minute at continuous hashing that it in all volume of liquid was identical.

That at which the course of the main valve will make 0,1 mm is accepted to temperature of the beginning of opening of the valve.

The thermostat needs to be replaced if temperature of the beginning of opening of the main valve is not in limits of 81+5+4 °C or a valve stroke less than 6,0 mm.

The simplest check of the thermostat can be carried out to the touch directly on the car. After launch of the cold engine at the serviceable thermostat the lower tank of a radiator has to heat up when the arrow of the index of temperature of liquid is at distance of 3-4 mm from a red zone of a scale that corresponds to 80-85 °C.