Pneumatic / vacuum central door locking: advantages?
 

Anyone knows if they are that, contrary to electrical systems, a pneumatic / vacuum central door locking works:
* even if the battery is dead?
* even if the car is flooded / submerged, i.e. the electrical system shorted?
* and / or else?

As it is actuated pneumatically, by an electrical pump, ... no it will not work without electricity.

The earlier cars worked from engine vacuum.

I read somewhere that MB felt that in an accident where the battery is damaged (cracked open, for example) the actuators would still work. With the older rubber-cased batteries, this happened quite often.

I think they are just quieter. Some other German cars also use similar systems.

If you need to open the door after an accident, from the inside, you open it. From the outside it is unlikely that a rescuer will have a key.

Well, on my car, the driver's lock also opens the passenger's lock, so MAYBE this might come in handy in an emergency.

Maybe, but if there's no electricity, the driver's lock won't open anything except the driver's door.

Audi, Volkswagen, Mercedes, others used a single-point pump and pneumatics when they introduced their central locking system. Most of Asia and Detroit used solenoids. Some like Land Rover use motors. They all work and they all require electricity.

Unlike some people's beliefs, your windows and locks will probably work fine with the car immersed. The water (especially fresh water) will not "short out" the 12v electrics, although salt-water will make short work of electronics. The pneumatic pump for the locks however, is designed to compress air, not water, and any water ingested in the pump will stall it so perhaps the electric solenoid version is better?

Either way, the doors of the car will open from the inside when locked. The rear doors will not, but the buttons are on the forward end of the doors to be accessible to the driver and not short-armed children in the back seats. I think it's a good design.