Rear AirMatic issue - 07' S550 4matic

  mercedes/s-class/2006-2013

Drove to work this morning, no issues. I drove home for lunch today and on my way down my driveway, the rear sounded and felt stiff. I got out and saw both sides of the rear were lowered, Im guessing all the way, top of the rear tires behind the wheel well. Low rider! lol. Front was fine. I hooked up Star and ran the pneumatic tests. The pump and front level control valves passed, the rears both failed for the level control valves. I ran all the other tests and they all passed, including pump and leak tests. I then noticed you can manually go into each strut and add or bleed air to them. To my surprise I was able to pump the rear up. I re ran the tests and the rear passed this time. I left it for 10 minutes and it seemed to hold. Then I drove up the driveway and back down, a 30 second drive at best. When I returned to the garage, the rear was almost back to the floor again. Do I need new struts? Is it both of them? Big job or can I DIY? I was quoted $1800-2000 for both from a nearby mechanic. Im a newbie to Mercedes vehicles.

I pumped the rear back up via DAS again and let the car sit. It has been sitting in the garage for over 18 hours now and the rear has stayed up and level. What the heck? Maybe the struts arent bad but something else linking the two is?

I appreciate all your feedback and help with this. I would love to tackle this myself.

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