To make your car usefull untill you can get it repaired you can by-pass the door lock leak. Follow the large supply line to the booster, follow the small line teed before the vacuum check valve. The lines will turn into a number of tees and check valves feeding as many as four systems (depending on the year model); door locks (yellow), A/C (green), shut-off (brown) and cruise control (black). Take the yellow line from the source and pull the hole. If the leak was in your doors that will eliminate the leak. The car should shut-off.
If that doesn't work try the blocking off the green, then the black till all you have is the brown. If it still doesn't stop then the vacuum diaphram in the injection pump is probably the problem (sometimes its the vacuum switch on the steering lock/ignition).
I would block each leg till the system works then replace them one at a time while seeing if it still works. We often see leaks in both the A/C and door locks. The 240D can actually work alright without the vac systems if you don't mind manual locks.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician