The vac lines under the hood have nothing to do with the locks. Open up the channel on the right side of the passenger floor; plug your mityvac in there to each vac line one at a time and determine where you have no vacuum. Then trace that line. You may have to replace a door lock actuator or just a rubber connector - or you might need to replace the pump. Sounds like the pump may be OK. I replaced two door actuators in my 300SD and all the locks work again.