it works when the engine is started. You are corre ct, it works from the power steering pump, and uses a special hydraulic fluid. I would recommend speaking to your dealer, and keeping a spare can in the trunk. Periodically look at your rear wheels, on the inside, and you can see the lift, which looks like a large shock, and pay attention to see if it is leaking. On my '89 750il, the shock mechanism was $900 per side for the part. If it leaks out a lot of fluid, use your spare can, because the use of anything else will be a serious mistake, likely ruining the system. You can see it lift the car just after starting up the engine, as the system builds pressure. It further adjusts the tilt of the vehicle during speed, and you can also watch it work if the motor is running and you load up the trunk. After a while, you may feel that this is a clever engineering marvel, but it costs a LOT when it is sick. Further, avoid the temptation to replace the system with non leveling shccks. There are design elements that only can be plugged to remove the sytem, leaving behind a power steering sytem that no longer works correctly.....ask your dealer mechanic. Just a few thoughts from a guy who put 225k on a 750il with such a system. Sold it for a normal 740i

david