Also check the steering damper for a "hard spot" at the center, they can get bent or otherwise damaged and get very stiff right at the center of travel. This can cause terrible steering vibration, too, when you hit a bump and the damper "bounces" instead of damping.

A bad idler arm usually causes wander, but I'd check it too, just to be sure. New busings are a great deal cheaper than a new steering box....

The "second correction" is because something is stiff and you are turning too far while forcing it over, and the steering box cannot pull it back. This can be a steering box valve problem (loose torsion bar comes to mind for US style boxes, I have no ideal how Benz does theirs!), but is more likely a stiff suspension part.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!