- 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.
Adding BMW concentrate
Example: As a result of the hydrometer measurement, it was found that frost protection is provided down to -10°C. In this case, it is necessary to drain 3 liters of coolant and add 3 liters of pure concentrate. The table applies to a cooling system capacity of 10.5 liters (320i, 325i). On all other models, the values are reduced by approximately ⅓.
Caution: Top up only with BMW recommended nitrite-free antifreeze.
Close the radiator cap and after a test drive recheck the frost resistance of the fluid.