Hi all...

84 380SE with Self Leveling rear.
The rear sags quite low overnight (wheel arch slightly covering tire), also the "whistling" sound from operation of the relief valve (in the level control unit) are evident sometimes. Height is restored about 1-2 mins after engine starts.
After researching on the forum and MB CD-ROM, I come to the following initial conclusions on one or combination of the following problems:

1. Mis-adjustment of the connecting rod on level controller.
2. Faulty Level Control Valve.
3. Sagging Springs.
4. Collapsed Differential/Sub-frame mounts.

The following are my thoughts:
If the differential/subframe mounts have collapsed, this should only cause slight sagging and perhaps interfere with the level controller.

The whistling noise indicates opening of the relief valve, and therefore level is continuously regulated too high. Perhaps an attempt to raise height by adjusting connecting rod by previous owner.
The sagging seems to be caused by sagging springs as well as a partially faulty level controller, which allows oil pressure in struts to drop beyond basic pressure. Because if spring only is at fault, height would retained by the pressured struts. But if level controller only is at fault (low/no pressure in struts, springs not sagging), would the springs alone be able to hold the car up at normal level (or slightly below)?

Please respond and any comments are welcome.
Thank you in advance for your help.

Best Regards,