Ever since I've owned my '82 300SD, the vacuum locks haven't worked. It sat in my garage for the longest time, so this was a nonissue. However, now that I'm actually parking this vehicle out in public, the fact that I cannot lock the doors is now an issue. It baffles me that the lock cannot simply be pushed down (or maybe there is something horribly wrong with my vacuum system.)

When I push down the driver's door lock, I hear the vacuum pump in the trunk come on. However, I cannot push down all of the locks. I think 3 out of 4 is the best I can do. Should I be able to lock all the doors manually?