During the operation of the car, check and, if necessary, restore the coolant level in the expansion tank, which should be 25... 30 mm above the mark «MIN». Checking and topping up the liquid should be carried out only on a cold engine.
With a working cooling system, over time, the liquid level decreases due to the evaporation of water, and the density increases. Therefore, before topping up, you should check its density with a densimeter. If the density is higher than normal, add distilled water. If the density is within the normal range, add the same fluid to the expansion tank as the system is filled with. When the liquid level is constantly decreasing and frequent topping up is required, visually check the tightness of the hose connections and fastening of the system devices. Eliminate leaks at hose connections by tightening the hose clamps. Leakage of coolant under the pump gear pulley should be eliminated by replacing the pump seal, which requires the removal of the engine and its partial disassembly to remove the pump.
If necessary, pure water can be added, which raises the freezing point of the liquid. Therefore, as soon as possible, repair the system. It is forbidden to add water at negative ambient temperatures.