There is a thumping sound coming from what seems to be under the cargo floor or back seat...but from the passenger side. It doesn't happen all of the time. If you feel the lines from the leveling system's reservoir under the hood, you can feel a thump that seems to correspond to the thumps you can hear.

I had seven adults in the car on a coast trip recently. Seemed to stay level and didn't sag at all.

Any ideas?

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2004 E320 Wagon W211
2000 CLK430 Convertible W208
1985 300SD W126
1983 300D W123