Most air ride systems a solenoid on each bag. Probably has a retaining clip that pops off first, then the solenoid twists out. The car must be jacked up first or it will drop like a rock. One trick is to jack up the car a little, that way the it thinks its too high and it will vent the system, possibly all the way before it errors out.

Mike. The Conti vented all sides, not just left. It was actually for two reasons. To vent to a lower position to help stability when parked (such as being brought over on a car ferry) and to also exercise the system so it would get use. On later Contis only the rear had air-ride. The Mark series always had it on all four corners.

Conversions, as mentioned, are always a possibility but it will impact ride quality for better or worse. Conventional thinking says bags are worse for handling but tests have show they are the same if not better than springs. If cost is a factor, I would ditch them. And never buy used bags, they will crack in no time. For a Mark VIII rear bags are just $100 each new from Arnott industries.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car