The Mercedes Benz W116, a classic sedan from the 1970s and early 80s, remains a sought-after vehicle for enthusiasts and collectors. Owning a W116, like this 1980 280SE with its robust DOHC M110 inline-six engine, often means embracing a hands-on approach to maintenance and repair. While potentially showing deceptively low mileage like this particular model, these cars, despite their solid build, can present owners with common issues that are well within the realm of a competent DIY mechanic.
One frequently encountered problem in the Mercedes Benz W116 is the notorious AC servo. Alongside a typical radiator leak, a cracked and leaking AC servo is almost a rite of passage for W116 ownership. The original author quickly discovered the aftermarket’s awareness of this issue, highlighting the thriving cottage industry surrounding this often problematic part. Instead of opting for potentially unreliable or temporary fixes, a robust solution was found in an aluminum-housed servo from George Murphy. Installing this upgraded part, along with a thorough clean-up of the corrosive coolant spilled by the old servo, is a recommended approach. Murphy’s excellent guidance further enhances this repair, making it a worthwhile investment for any W116 owner facing this issue. The auxiliary coolant pump, located near the AC servo, and the amplifier behind the dash were also addressed during this phase of maintenance, ensuring the cooling and electrical systems were in top condition.
Vacuum leaks in the door locking system are another common quirk of the Mercedes Benz W116. Diagnosing these leaks can be an interesting exercise. A telltale sign is if the door lock plungers slowly drop after the car has been left unlocked for a period. Locking the car then reveals if the leak is in the diaphragms that control the locks. A further diagnostic clue is the gas door lock potentially sliding open again after locking due to vacuum loss, a design feature to prevent being stranded without fuel access. In this case, the rear passenger door actuator was identified as the culprit, temporarily remedied by plugging the vacuum line while awaiting a replacement part.
Replacing the trunk seal on a Mercedes Benz W116 is a more involved, but necessary task to combat water leaks. Using 3M Weatherstrip Adhesive after meticulously cleaning the old adhesive channel is crucial for a proper seal. The author’s experience highlights the challenge of replicating the factory precision of Sindelfingen, particularly with the seal’s complex design featuring joints and a specialized section for the rear deck lid. The seal’s “curl out” lip, designed to channel water, can become compressed over time, leading to leaks even if the seal appears visually intact. The process is described as time-consuming, requiring patience and techniques like applying the seal in sections and removing the lower plastic shield for better access around the taillights. Vinyl gloves become essential to manage the adhesive and maintain cleanliness.
The struggle with the new trunk seal illustrates the nuances of classic car restoration. The new rubber’s “grabby” nature and tendency to fold incorrectly required inventive solutions beyond talcum powder. The resourceful use of strings, and later ribbed rubber cord intended for window screens, to pull the seal lip into the correct “curl out” position demonstrates the problem-solving often needed in W116 maintenance. This detailed account underscores the commitment required to achieve a truly dry trunk in a W116.
Addressing a slipping odometer is another typical Mercedes Benz W116 repair. Accessing the instrument cluster involves careful removal, emphasizing the importance of taping the dash and protecting the steering column to avoid damage. Loosening the speedometer cable beforehand eases removal. Plastic trim tools are recommended to prevent scratches during this process. The cluster gasket’s condition should also be checked and replaced if necessary, as was done using a salvaged and reconditioned gasket in this case. Referencing online guides like Dieselgiant.com is invaluable for odometer repair. The common culprit is identified as a pot metal gear slipping on its shaft. The repair involves pushing out the shaft, roughening the end to increase friction, and re-seating the gear. While Loctite application proved difficult, the increased friction from roughening the shaft sufficiently resolved the slipping issue. Cleaning and testing the instrument cluster lights before reinstallation ensures all aspects of the unit are functioning correctly.
Post-repair reflections bring a pragmatic perspective. The author notes the 280SE’s fuel economy is comparable to a larger 450SE, yet with less power. This observation highlights the trade-offs inherent in choosing different W116 models. Future maintenance plans include valve adjustments, new tires, steering box adjustment, and windshield replacement, demonstrating the ongoing nature of classic car ownership. Finally, the mention of a hot start issue and late transmission shifting opens the door to further troubleshooting and community advice-seeking, particularly regarding the fuel pressure accumulator as a potential cause for hot start problems.
In conclusion, this account provides valuable insights into common Mercedes Benz W116 ownership experiences and DIY repairs. From AC servo replacements to odometer fixes and trunk seal intricacies, the narrative underscores the blend of challenges and rewards in maintaining these classic sedans. The preference for the rarer 280SE over the more common 450SE adds a layer of appreciation for the unique aspects of each W116 variant and the satisfaction derived from keeping these pieces of automotive history on the road.
