Originally Posted by psfred

Check the upper strut mount, it may have sheared off. It's trapped by the flange underneath and the plain steel (not black) plate on top, and will thump between the two "safey plates" rather alarmingly if the rubber parted company.

If it did, replace both, the other won't be far behind.

If it's fine, check sway bar bushings and mounts (if like the W124, they can break off and thump). Next, look at strut mounting bolts, control arm, and check ball joint, although I'd not expect that to thump while "pumping" the fender.

Most likely, with a helper, you can find the offending part by putting your hand on the various suspension parts while helper "pumps" the fender. WATCH FOR PINCH POINTS!!! There are various placed where clearance will vanish as the suspsenion moved, can crunch a finger or two!

It's also possible a coil has broken off the bottom of the spring, too.

Peter