When troubleshooting your vacuum system you must know where the hoses and lines go
What's wrong with my Mercedes?
A very common problem that requires precise troubleshooting
#1 Failure Point are the rubber diaphragms in the door lock actuators
Pump mechanisms breaking apart and piston bolt failures
Easy to test when out of car. See Kent's manual to learn how to test without removing door panel.
Common concern on 1980 to 1985 Mercedes Diesel 240D, 300D, 300CD, 300TD
Double check for damage and use a product to scare them away
Look for the cause in the drive mechanism