Your coolant circulation is provided by the Mercedes-Benz Water Pump located on the front center section of your engine. This is a mechanical pump that draws coolant from the radiator and distributes it into the engine block so a constant temperature of your engine can be maintained.
The makeup of your water pump on your Mercedes-Benz consists of an impeller on a shaft that is encased in a housing. There is a coolant inlet on the bottom and an outlet in the back leading directly into the engine block. Where the shaft and the housing met on your waster pump is a polymer seal. This is the component on your coolant pump that will wear out over time and cause it to become faulty. When this seal is ruptured, a small coolant leak will begin to emerge from a hole in the bottom of the Mercedes-Benz Water Pump. The owner of the Mercedes-Benz will notice this has happened because of the coolant puddle that will appear on the pavement in the forward area under their vehicle.
In most instances the coolant leak on the water pump cannot be seen directly because the pulley on the water pump shaft is too large and covers the hole where the coolant is exiting the housing. The harmonic balance is also in the visual path of observing the hole from the bottom of the pump. Both of these pulleys will be wet with coolant and the only possible source is the seal on the pump is leaking.
When the seal goes on the water pump, the entire unit has to be replaced. Not only is coolant leaking from your system, but the shaft on which the seal is on will begin to move. This could cause an imbalance in the drive belt system on your Mercedes-Benz.