2004 Mercedes E320 wagon

My 2004 E320 has a distinct thump in the left rear tire area when I go over any bump. Could this be a bushing problem or perhaps a strut problem?

Unlikely, but possible of course. Unless your wagon has lived a hard life, a 5-year old Merc should not have rear suspension problems yet. Get it up on a lift and have a look-see. Is it possible that it’s the spare tire not fastened down and bouncing you hear?