jensbenz,

The USA version of the '88 300 SEL never came with the rear hydraulic self leveling option. But on the USA 560SEL it was standard system. See this link for a picture of the accumulator/air cell.



http://catalog.peachparts.com/ShopByVehicle.epc?q=1988-Mb-560sel-Suspension&yearid=1988%40%401988&makeid=MB%40%40MB%40%40X&modelid=560%2DSEL%2D001%40%40560SEL&catid=L%40%40Suspension&subcatid=L7040@@Accumulator&mode=PA




And yes if these go bad you will loose rear ride height and get a harsh ride.

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BENZSTER

W123, '81 240D, Pastel Grey/Blue Tex
W126, '88 300 SEL, Artic White/Grey Leather