Check the first post in this thread.
OZBENZ - Australian & New Zealand Mercedes-Benz Forums • View topic - Let sleeping dogs lie.

The hose at the rear of the engine can leak. The coolant will drip down the side of the engine, onto the crossbar under the engine and drip off near the passenger side wheel.

Check underneath the hose for a leak.

There's also a rubber grommet on the engine attachment.