Figure 149. Checking the coolant density: 1 - expansion tank cap
Before the onset of cold weather, it is necessary to check the degree of frost resistance of the coolant. To do this, open the expansion tank cap and use a test device to remove some liquid. The device shown in the figure 149, just one of many similar testers. Other suction devices may use a rubber bulb. Using the scale of the device, as shown in the figure, or using the position of the float on other test devices, determine the density of the coolant and, if necessary, add the required amount of antifreeze.
Note: Mercedes recommends using only certain brands of antifreeze. If in doubt, contact a service station. This is especially important if the car is still under warranty: non-recommended fluids can damage light alloy engine parts or the radiator.
Information copied from the website MercedesMan.ru