Table of contents: Checking the coolant level ↓ Topping up the coolant ↓
In the cooling system at operating temperature there is excess pressure of 1.2-1.5 bar, which significantly increases the boiling point of the coolant above 100°C. At the same time, a certain reserve is provided. The engine can heat up to a temperature above 100°C without the risk of boiling of the liquid in the cooling system. To maintain the correct pressure in the system, the expansion tank is equipped with a cap with a safety valve (1.2-1.5 bar) and vacuum valve (0.06-0.1 bar). The vacuum valve lets air in when the coolant decreases in volume as it cools.
Checking the coolant level
Although there is a coolant temperature warning light, you should not rely on it entirely and should check the coolant level in the expansion tank in the engine compartment from time to time.
The correct check of the coolant level can only be done with the engine off. The fluid level is visible through the transparent tank even with the lid closed. When the engine has cooled down, it should be at the level of the arrow point on the side of the tank, and if the car is new, at the "min" mark of the expansion tank.
When the engine is warm, the level should be slightly higher.
Topping up the coolant
A noticeable loss of coolant indicates a defect or damage. Coolant is not consumed or evaporated from a closed cooling system. Only when the engine overheats can a small amount of coolant escape through the expansion tank cap.
When opening the expansion tank cap on a warm engine, there is a risk of injury from hot steam, so you must proceed with caution.
Turn the cap through a rag or glove first one turn and release excess pressure in the cooling system. Only then completely unscrew the cap.
If water is added, the coolant will gradually become diluted, so it is necessary to add coolant.
Do not add liquid above the mark, as the liquid expands when heated and the excess flows out of the system.
Small amounts of liquid can be added to the tank both when the engine is warm and when it is cold.
If there is a significant loss of fluid and the engine is warm, do not add cold fluid to the expansion tank, as this may cause the cylinder head to warp or the cylinder block to crack.