Alright, when I let the 500E sit in the garage overnight (12 hours or so of rest for it), and i get up in the morning to drive it. When I start her up she runs fine. Then I back out of the garage, as I do so and turn my wheel, something makes a loud noise, loud enough to hear both in and out of the car. If I don't turn the wheel it doesn't make the noise. It's a loud buzz/hum noise. It only does it for about 1/4 a mile and then it stops once the car is warmed up. If I park her for 4 hours or so then come back, she still won't do it again. Only when I let her sit for about 8+ hours. It's whenever I turn the wheel left or right it does it, if its going straight, I get nothing. A new steering box was put on recently, but if I'm correct, it was doing this before and after the box was put in. I can't remember if it was doing this when I first got the car or not. Is this something normal or is something wearing out?

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Own:
2013 C300 4matic
2009 C300 4matic

Owned:
2001 E320 Sport
1992 500E
1989 300SEL