The brief
The 216d had developed a small pull to the left in the steering and a clunk over speed humps, and on a quick look under the front the owner had spotted grease tracking down one of the ball-joint boots. He brought it in.
The front lower control arms locate each front wheel through a ball joint at the outer end and rubber bushings where they meet the body. When a ball-joint boot tears, the joint loses its grease and starts wearing; when a bush goes soft, the wheel can shift a fraction under load. The pull is the geometry drifting off, the clunk is the slack on bump impacts, and the grease you can see is the boot that has already given up.
The diagnosis
That grease leak was the giveaway: the lower arm's ball joint on that side had a torn boot and was running dry, well on its way to play. A pry-test on the bushes showed both arms deflecting past the service limit, not just the leaking side.
Replacing one arm and leaving the other would have left the front feeling lopsided side-to-side, and meant a return visit when the second one followed the first. So this was a pair job, both front lower arms renewed together with fresh ball joints and bushes.
The work
Both front lower control arms came off, and a matched pair of new BMW-spec arms went on, complete with new ball joints and bushes, every fastener torqued to the manual figures with the suspension at ride height so the bushes settle in their neutral position.
Then the car went onto the alignment rack for a full four-wheel alignment, camber, caster and toe brought back to factory, with the before-and-after numbers printed for the owner.
The outcome
The steering pull was gone, no more clunk over humps, and the alignment back in spec across all four corners.
The 216d went home tracking straight and feeling solid again rather than loose and pulling. For the owner that is a car that holds its line without constant little corrections, plus, with the geometry restored, front tyres that will wear evenly across their tread rather than being scrubbed away on one edge, which is a full set's worth of kilometres saved.