5.1.2. Antifreeze - a security measure from freezing The cooling system is all the year round filled with mix of water, antifreeze and rust-preventing agent. It interferes with a rust and corrosion, adjournment of salts and, besides, increases temperature of boiling of cooling liquid. In the cooling system because of expansion of liquid when heating excessive pressure is created that also leads to temperature increase of boiling of cooling liquid. Pressure is limited to the valve located in a cover of a broad tank which opens with a pressure of 1.4 - 2.0 atm. For faultless functioning of the cooling system it is required to be insured from boiling of cooling liquid at which the steam stopper therefore circulation of liquid decreases can be formed and cooling of the engine worsens. Temperature of boiling has to be increased. For this purpose the cooling system always has to be filled with mix of water and the listed additives to it.