The brief
The E200 had a knock from the front over bumps and the steering had gone vague, the signs of worn lower control arms. He brought it in. That's the kind of issue every owner of these should know about, because the play only grows and it takes handling and tyre life with it. The lower control arms locate the bottom of the front suspension, with rubber bushings at their pivots and a ball joint at the outer end. As the bushings age they crack and soften, and once there's play in them the wheel moves around more than it should, so you get the knock over bumps, the vague feel, and uneven tyre wear. Worn control arm bushings don't recover, 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 knock and the vagueness. The rest of the front suspension 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. 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 knock was gone, the steering tight and precise, the car tracking straight.
The outcome
Tight, precise steering, no knock from the front, the car tracking straight, and the alignment set so the front tyres wear evenly. The E200 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.
