When the plug is closed, the sealing surface fits tightly against the edges of the expansion tank opening. Air cannot escape, and the pressure is maintained.
When heated, the pressure in the cooling system increases and at values of 0.9-1.15 bar (for models before August 1978.) or 1.2-1.35 bar (for models produced after August 1978.) the relief valve opens. Now a small amount of air and steam can escape to reduce the pressure.
When the temperature drops, the coolant decreases in volume, and a vacuum is observed in the cooling system. To compensate for the vacuum, a second valve is installed in the plug. It opens at a reduced pressure of 0.06-0.1 bar, allowing outside air to enter the cooling system.
Note: Models manufactured before July 1978 used a plug, a safety valve, which opened at a pressure of 0.9-1.15 bar. Such plugs are no longer manufactured. Currently, plugs are manufactured that open at a pressure of 1.2-1.35 bar.
Visitor comments