The brief
The E250 had the steering wheel vibrating, badly, when turning or braking, the kind of shake that tells you something in the front suspension has gone loose. He brought it in. The culprit was the front lower control arm bushings. The lower control arms locate the bottom of the front suspension, and rubber bushings at their pivots let them move and keep the joint quiet and precise. As the bushings age they crack and soften, and once there's play in them the wheel can move around more than it should, especially under the loads of turning and braking, which feeds vibration straight up through the steering. Worn control arm bushings don't tighten back up, and the play affects handling and tyre wear, so the arms need replacing.
The diagnosis
On the lift the front suspension got the once-over. The lower control arm bushings on both sides were cracked and worn with play under load, exactly what makes the steering wheel vibrate when turning and braking. The rest of the front suspension and the brakes checked out. When the arms on an axle have gone, you do the pair, and the bushings are pressed in, so the practical fix is complete new control arms rather than just bushings, then a four-wheel alignment.
The work
Both front lower control arms were unbolted and removed, and new genuine Mercedes-spec control arms fitted with fresh bushings and ball joints, every fastener torqued to the manual figures. With both sides back together the car went on the alignment rig and the front geometry set to specification so the steering tracks true and the tyres wear evenly. A road test confirmed the vibration was gone, the steering tight and steady through turns and under braking.
The outcome
Tight, steady steering, no vibration through the wheel when turning or braking, the car tracking straight, and the alignment set so the front tyres wear evenly. The E250 went home with the front suspension sorted. Worn control arm bushings only get sloppier and they take handling and tyre life down with them, so doing the pair and resetting the alignment put the steering back where it should be.