- A hydrometer, available commercially and at petrol stations.
The frost resistance of the coolant should be checked before the onset of cold weather, especially if clean water was added.
Warm up the engine until the upper hose connected to the radiator is warm.
Carefully open the expansion tank or radiator cap, see section "Checking the coolant level".
Fill the hydrometer with liquid and use the float scale to determine the density of the liquid. In our latitudes, protection from freezing down to -30°C must be provided.