Front sway bar mounts. They are shrunken and the sway bar is rattling on the ends. Take a peek, dollar to a donut the rubber isn't tight on the bar. If not, replace. It's not a bad job, you can do it with the car on the ground. You will need to turn the front wheels to get good access to the outer ends.

Use some silicon lube for the frame bushings, you will probably have to drive at least one on. The old ones will fall off.

Check the frame mounts, too -- they have a tendency to break at the base, allowing them to rattle terribly. This will NOT be obvious, you must pry on them to see it.

Ball joints will also rattle, and I would recommend a new control arm since it's likely the bushings are bad, too, and they are a real PITA to replace. Try the sway bar first.

If the rubber in the strut mounts is cracked, replace them. You do not have to remove the strut, but you will get a good workout! Jack car to give you room, but leave the front wheels (or wheels) on the ground -- the spring can fly out otherwise! You can put it up on jackstands and jack on the control arm, but this is difficult on the W124, the jack slides too much. Remove the struck nut (you will need a 7mm allen to counterhold, and this is NOT in the usual assortments...). Remove the three nuts that hold the mount in place, then collapse the strut and pull the mount off, insert the new mount, and re-install the nuts and strut nut. It may take two people to push the strut down and hold it, it is VERY strong! I got pretty much worn out.

An alignment afterwords is in order.

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!