I just recently went through something like this. When ever I would turn the wheel I would get a creeking, groaning sound. Also when ever I got out of the car, I would here it as the body raised up. It turned out to be the driver's side balljoint. My mechanic said this is very common for the W116, and W126 cars. Particularly in the spring. He said during the winter the road salt and sand work their way into the joint and start grinding away. Since I had that replaced, the front end is silent again and my steering is a little tighter. As I learned, the balljoints are generally not a DIYer. At least for the W116/W126 cars, it requires a special tool to pull out and to press in the new balljoint into the spindle.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member