Yikes. So it seizes, breaks the timing chain, and the pistons smash the valves at max lift. The BMW engineering analysis probably determined that driving the pump off an external aux power belt was too unreliable and risky. What a brilliant design!
Germany engineering at its finest.
I’ve had vacuum pumps fail on me ... on Lycomings... but on aircraft the vacuum pumps use graphite impeller vanes that are self lubricating and run off a jackshaft... absolutely no chance of engine damage when one fails..