Your car probably has the same system that is on my both of my TDs. You should able to locate the hyd. fluid res., somewhere towards the front of the engine bay. There shuold be some sort of arrow marking to mark the full point. The level controler should be located in around the rear diff. It should be an aluminum box with an arm attaching itself to the rear sway bar. I would strongly recommend not messing with it with the car sittin of the ground. Put the backend on a set of ramps. This way should it suddenly lower, you won't get hurt.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member