The door locks on many W123 Mercedes Benz are locked and unlocked using vacuum produced by the vacuum pump on the engine. Leaks in the door lock system can cause the door locks to operate poorly. One common item that leaks is the vacuum operated lock actuators. The main "moving part" is a set of rubber diaphragms that, with age, get brittle and crack. With this guide, you will learn how to repair these actuators if you have the early style, with four vacuum diaphragms.