Your vacuum line is broken or split. I believe it enters the pasenger compartment through the firewall in the vicinity of the fuse box. I think there is a y connector there. Follow that line to the engine to determine the vacuum source take off. If you can pull the connector apart, try that, with the engine running to see if you have mainfold vacuum at that point. If you do, then your problem is inside the car. May have to remove the cluster to find it.
1987 BMW 325