I have an 98 ml320. Recently, what I think is maybe the heater pump/moter is making a bad noise randomly while driving. Sometimes it continues after the car is turned off. Sorry for the lack of info but I'm a woman trying to trouble shoot my car. Its next to the battery and has hoses coming from it that go to the dashboard.The noise reminds me of when the impeller in my fish tank filters needs cleaning. Kinda a humming squeek sound. If I wiggle the unit, it stops.