Hard Ride = Nitrogen Accumulator, '94 Wagon, Symptoms??
 

My '94 E320 wagon with 91K miles on it recently started riding like a truck, i.e. very hard! In searching the forum, this car has a load leveling rear suspension, and a reported symptom of a hard ride can be caused by the nitrogen cells going flat. There is ample hydraulic oil in the reservoir and no leaks.
I'd really appreciate confirmation from an expert before installing new Nitrogen cells. Many thanks!

Yes, the "cells", AKA Accumulators, are necesary for a proper ride. If they lose pressure or the diaphragm ruptures, there is nowhere for the hydraulic fluid from the dampers to go when you hit a bump, so your suspension is effectively hydrolocked. It will ride like a corvette.

babymog is correct. Replace the accumulators---you will be amazed at how well controlled the ride is on a fresh set of accumulators. Mark

accumulators
 

I got a 94 as well ,and they were replaced originally at 90,000 miles , and 2 weeks ago replaced them at 180.000 miles, so yeah 91k miles sounds like
you need to replace yours,lou