The Mercedes-Benz W115, a classic saloon known for its robustness and elegant design, incorporates a vacuum-operated central locking system. For owners of these vintage vehicles, issues with the vacuum locks can be a common yet solvable problem. Diagnosing and repairing these systems yourself is indeed achievable, although the complexity largely depends on the location and nature of the leaks.
Understanding the Mercedes W115 vacuum lock system is the first step in effective troubleshooting. Resources like Ken Wheeler’s manuals at Mercedes Source offer invaluable guidance on system testing. Additionally, the Mercedes factory shop manual, specifically section 80-901 for the W115, provides comprehensive vacuum system diagrams essential for pinpointing issues.
Alt text: A classic Mercedes W115 240D saloon car, highlighting its iconic design and relevance to vacuum lock system discussions.
If your vacuum lock problems stem from deteriorated rubber diaphragms within the vacuum actuators – of which there are five in the central locking system – you may be in a relatively straightforward repair situation. It’s crucial to systematically test each component. Begin by removing the actuators, using golf tees to temporarily seal the hoses, and then methodically testing each vacuum line. The vacuum lines themselves are constructed from a rigid plastic that becomes increasingly brittle with age and temperature fluctuations. Mercedes-Benz ingeniously designed accessible sections, particularly in areas prone to flexing like door jambs. However, accessing tubing in other areas might necessitate removing interior trim pieces such as interior B-pillar trim, rear seatbacks, and plastic door thresholds.
Alt text: A close-up view of a Mercedes W115 vacuum actuator, showcasing the component responsible for the central locking mechanism and highlighting potential diaphragm failure points.
A vacuum tester becomes an indispensable tool for accurately locating leaks throughout the system. Thorough testing across the car will give you a clearer picture of the scope of the repair work needed. In one instance, after replacing all actuator diaphragms, persistent leaks were traced back to fractured sections of the plastic vacuum hoses. At this juncture, prioritizing other critical repairs led to postponing the vacuum lock project. A comprehensive solution, such as rerunning all the plastic vacuum hoses, can be integrated with larger interior refurbishment projects, like carpet replacement.
Alt text: Diagram illustrating the vacuum hose routing within a Mercedes W115, emphasizing the complexity of the system and potential locations for leaks in aged plastic lines.
Beyond central locking, the W115’s heating and air conditioning system also relies on two additional vacuum actuators for its operation. These are accessible from under the dashboard. For improved access and comfort during the often physically demanding process of accessing these components, removing the front seats is highly recommended.
In conclusion, while repairing the vacuum locks on a Mercedes W115 can present challenges, a methodical approach to diagnosis, utilizing available resources, and understanding the system’s components will empower owners to restore this convenient feature of their classic Mercedes.
