I recently bought a 2014 GL 450. After driving when I turn off the engine, I hear what sound like a small electric motor continuing to run and antifreeze/coolant starts leaking from the front driver's side of the engine. But only about 1/2 of the coolant leaks out not all. When the vehicle is not on and I fill up the coolant reservoir, nothing leaks out, neither when I am driving. Only when I turn the engine off. Any clues or help would be appreciated. The leakage does not seem to be coming from the water pump, Thank you