The condition I am talking about occurs after one drives the car for long periods with the accumulators "water logged".
The term "water logged" refers to the condition in home wells where your reservoir has lost its air cushion. If you have never been on a well you won't recognize the simile.
To understand the hard ride one must understand the concept of accumulator, nitrogen chamber, GAS SPRINGS. The chamber comes with high pressure Nitrogen gas pressing the internal diaphragm to the sides of the ball. The system receives pressure from the pump which builds against the diaphragm. When the pressure is greater than the Nitrogen base pressure the diaphragm is lifted off the surface and the Nitrogen is compressed. At some point as the Nitrogen is compressed the overall pressure lifts the car. The struts are now held up with the pressure that is bouncing on the Nitrogen sac. When new this may leave half the total chamber size for compression. As the time goes by the gas leaks through the membrane and the chamber size at pressure is reduced. Eventually the gas is gone and the pressure is against the walls of the container solid. Similar to a spring bottoming out.
After bottoming out over every white line for a while the system manages to beat all the fluid from the system and the car goes low and bounces like a ball. I have seen the condition many times. If the shocks aren't leaking these systems seem to work all right after accumulator replacement and fluid restoration.
Bosch Master, ASE Master, L1
33 years MB technician