Okay, after some research, and by pure chance watching an MB Technical overview on you tube on the w124 cabriolet last night, I found out that tha cabriolets have 3 vibration dampers installed, the big one on the left front shock tower, one in the left trunk well and lastly the third is in the center windshield headrail.

To access the damper in the headrail, do the following:
1. Remove dome light surround by yanking off rear view mirror, prise out the map light lenses from the rear face to uncover 2 mounting screws. Remove the 2 aforementioned console mounting screws, as well as 3 screws holding the metal rear view mirror mounting base. Let the console hang on the power wires. Look up in the center of the exposed headrail metal and you will see a black metal spring clip, more on that later

2. Losen the 2 visor clips, no need to remove, just loosen 1/4 inch to relieve pressure

3. Remove to 2 roof latch plastic trim surrounds on the top of the headrail, the receiver end where the top clasps into. To remove these, fully remove mounting screw and then pull laterally towards the outside side of vehicle, there are small "L" tabs on the underside that can snap if not careful and pull out to the side.

4. Peel back exterior APillar rubber weatherstripping at the top of the A pillar by the headrail top vinyl cover, this will expose 1 screw on each end that secures the headrail top cover. Remove these carefully with a magnetic screwdriver to ensure it doesn't fail into the pillar.

5. Carefully prise the top headrail cover upwards from each side, carefully working it out of the rubber front window seal as well as rear plastic trim around the top latch handles. Once you near the center of the headrail you will then need to prise that exposed metal spring clip uncovered under the dome light console. Once the spring clip is freed, the headrail cover lifts freely.

6. With the headrail cover exposed you will see a lead bar about 10 inches wide mounted in a channel in the headrail. It weighs about 5 pounds. Tye bar is mounted in rubber isolators on each end. While mine were intact, they were also drooping a bit. I suspect that with a harsh shake such as going over rail road tracks, the vibration is too much for the aged mounts causing the damper assembly to contact the surrounding area and thus my rattle.

I chose to add foam tape weatherstripping, the home window and door stuff about 1/4 inch thick to the length of the lead bar on the bottom and beveled sides to isolate the bar from the headrail in a drastic scuttle shake.
You could renew the rubber mounts if they are still available, but if they are intact no real need to replace.

Whatever method yoh choose to use, do not affix the damper rigidly to the headrail or you negate the purpose of the damper, it must be free to flex within its mountsin order to work.

Installation is reverse of removal starting with the center spring clip first, and then working the cover carefully back over the trim and into the windshield seal.

While the cover is off, look at and lube the top latch assemblies, which incidentally come out this way as well, should theh need servicing, with the headrail cover off, they are fully accessible.

If anyone can suggest a good free image hosting site, please let me know, as photobucket is no longer available to me for this purpose.

Thanks

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)