My 1985 300TD has a vacuum leak. The engine won't shut down without using the manual stop and the door locks don't work. The brakes and transmission are working fine. Does the fact that the brakes and transmission are working while the shutdown and doors are not, help in locating the leak? Or, do I follow all the usual steps (as described in Kent's vacuum source leak detection manual)? [by the way, is it possible to search the forums?]