ADS hydro-pneumatic suspension failure
My '90 R129 500SL has ADS suspension. It seems to have stopped working. An independent mechanic has diagnosed that the electric pump in the boot/trunk is not functioning. He also spoke about a mechanical pump in the engine bay, but has not assesed its condition. A main dealer replaced the two rear "spheres" about twelve months ago. Driving the car is like driving on bricks. The nose bobs up and down like a seesaw. The heigth adjustment is not working. The hard/soft setting appears to still do something. I am not confident that anyone over here knows how to repair and setup this system, including the main dealers.
Any body familiar with this system?
Know which parts to replace?
Know the part numbers?
Hoping there is an expert out there. Please help...

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'66 W100 600 SWB
'05 W463 G55K AMG
'91 W126 500SEL
'93 W463 300GDL
'84 W460 280GES
'83 W460 300GDL
'66 W111 220SEb Coupe
'58 W121 190
'58 W180 220S
Have previously owned '99 SL600, '99 ML320, '79 450SLC, '79 450SEL 6.9 x 2, '68 600, '91 190E 1.8, '90 190E 2.0, '85 190, '90 500SL, '92 500SEL, '97 E300Turbodiesel, '91 300D, '72 280S, '82 300D, '81 300SD, '85 230E, '56 220a and I'm sure I'm forgetting some.