1989 560SEL Self Leveling Suspension Question

[tf114]

Hi All,
I just bought this car and it is my first experience with the Self Leveling Suspension System. On inspection there is no visible signs of leaks in the rear shocks. The system was nearly dry of hydraulic oil. My question is: Beside the rear end housing there is a unit where four fitted lines attach as well as a bleeder valve. Is this associated with the self leveling system, I checked all the manuals I can get my hands on and see no reference to this. Any suggestions or direction would be appreciated. Thanks in advance.