Expansion tank (VAZ-2109)

The expansion tank is made of translucent plastic and is secured with a belt to the brackets of the left mudguard of the body. The lower branch pipe of the expansion tank is connected with a hose to the thermostat. To prevent the formation of steam locks, the upper branch pipe is connected with a hose 4 (see figure 31) with a radiator hose located at the top of the radiator tank. The expansion tank has a filler neck closed with a plastic plug (figure 34) with outlet (steam) 4 and inlet 2 valves. The valves are installed in the plug in a separate non-separable brass block 5.



When the engine is running, with a sharp increase in temperature or boiling of the liquid, the pressure in the cooling system increases. This also increases the boiling temperature, as a result of which the heat transfer of the radiator increases. When the pressure in the system increases, the outlet valve opens and the vapors leave the tank into the atmosphere. The pressure at the beginning of the opening of the outlet valve is not less than 1.1 kgf/cm².



When the liquid cools down or drains, the pressure in the system decreases and atmospheric air is sucked in through the inlet valve. The excess pressure at the start of opening the inlet valve is 0.03...0.13 kgf/cm². To completely drain the liquid from the system, the plug from the expansion tank must be removed.

(The article is taken from the website: VAZbook.ru)