Warning! Do not attempt to remove the expansion tank cap until the engine has cooled down - you risk scalding. Do not leave the coolant container open for a long time, as it is poisonous.
1. There is a float in the expansion tank that monitors the coolant level. If the end of the float protrudes from the filler neck by no more than 20 mm, then the liquid level is normal. There is a plate with additional information next to the tank.
Prevention
A closed cooling system does not require regular topping up of the fluid. If you have to do this often, there are leaks in the system. Check the radiator, all hoses and connections for signs of leaks. If a leak is found, fix it as soon as possible.
Use antifreeze all year round, not just in winter. Do not add pure water to the cooling system, as antifreeze will lower the boiling point and raise the freezing point.
2. If you need to top up the fluid, wait until the engine has cooled down. Slowly loosen the expansion tank cap to relieve pressure in the system, then remove it.
3. Add the antifreeze/water mixture to the expansion tank until the end of the float rises 20mm above the filler neck. Screw on and tighten the expansion tank cap.