Draw some coolant from the expansion tank into the hydrometer.
The hydrometer is immersed to different depths depending on the specific gravity of the liquid.
The scale shows up to what temperature the protection against freezing is sufficient.
Some of the frost resistance testing devices are equipped with an arrow that indicates the degree of frost resistance.
Control of antifreeze concentration
In most cases it turns out that the concentration of the coolant is already insufficient. It is necessary to add a little antifreeze; approximately ¼ liter for every 10°C below normal.
Remove the lower engine compartment protection (chapter "Body elements").
Place a container under the car.
Open the drain plug at the bottom of the radiator or remove the bottom pipe on the radiator.
Be careful and cautious if the coolant is at high temperature!
Drain 1-2 liters of coolant.
Reinstall the tube or tighten the plug without pressing.
Add the appropriate amount of undiluted antifreeze and top up with the collected coolant from the container.