While the Mercedes-Benz W116 S-Class of the 1970s established the brand’s reputation for safety and engineering prowess, it was the subsequent W126 S-Class, launched in 1979, that elevated the model to true luxury icon status. This generation, and particularly models like the 1984 Mercedes 500 Sec, became enduring symbols of 1980s affluence and automotive excellence.
The W126 S-Class marked a shift towards aerodynamic efficiency and improved fuel economy. Its streamlined design boasted a 14 percent reduction in drag compared to its predecessor. Even with a weight around 3,600 pounds, the six-cylinder and diesel versions of this S-Class generation were remarkably efficient for their time, especially when compared to the large American sedans of the era. Safety was also paramount, with features like a driver’s airbag, introduced early in the model run, and a passenger-side airbag becoming available in 1989 and standard in 1990. Further advancements included traction control and seat-belt pretensioners, solidifying the W126’s position as a safety benchmark.
For the US market, the Mercedes-Benz W126 S-Class models can be broadly categorized into two periods: 1979-1985 and 1986-1991. During the initial phase, American buyers had access to the 380SE/SEL and 500SEL models, both equipped with V-8 engines. Following a comprehensive mid-cycle update in 1986, the US lineup expanded to include the 300SE/SEL (inline-six), 420SEL, and the range-topping 560SEL (V-8). The coupe versions, known as SEC models, were initially offered as the 380 SEC and 500 SEC, and later as the 420 SEC and 560 SEC after the refresh. It’s worth noting that the early 380 models, and even the 420 models to some extent, were often perceived as being hampered by emission controls. By 1986, the 300 models offered performance comparable to the earlier US-spec 420.
Diesel engines were also a significant part of the W126 story. From 1980 to 1985, the US received the five-cylinder 300SD model. This was followed by the six-cylinder 300SDL in 1986 and 1987, and subsequently the 350SD and 350SDL models in 1990 and 1991, ensuring the continued presence of diesel options in the S-Class range.
The mid-cycle update of the W126 not only brought a more potent engine lineup but also cosmetic and interior enhancements. The 1986-91 models are visually distinguishable by their flush halogen headlamps and integrated headlight wipers. Interior upgrades included electronic automatic climate control, an electrically adjustable steering column, and leather trim for the steering wheel and shift lever. Heated front seats were standard on the 560SEL and 560SEC and optional across the rest of the range. Notably, a luxurious two-place rear seating configuration became an option for the 500SEL and 560SEL for the first time. This option featured power-adjustable rear seats, a sophisticated burl-walnut center console extending into the rear, and plush Arametta (suede-like) leather upholstery. A 1984 Mercedes 500 SEC, while pre-facelift, still embodied much of this luxury and performance ethos.
Mercedes W126 powertrains are renowned for their robustness and longevity, frequently exceeding 200,000 miles without major issues. Engines often outlast transmissions in these models. While front-end and steering bushings and components will likely require replacement sooner, typical repairs are generally no more complex than those for other European cars of the period. However, parts costs can sometimes be a factor in overall ownership expenses. Vacuum-operated power locks can occasionally be problematic, exhibiting intermittent failures or slow operation. The climate control system, while adequate for its time, is less effective compared to modern systems, or even contemporary American luxury cars, and can be complex and costly to repair. For a 1984 Mercedes 500 SEC, these are points to consider for potential maintenance.
Diesel engines in the W126 family generally offer even greater longevity than their gasoline counterparts, although fuel-system issues can arise in colder climates or with infrequent use. The 350SD and SDL models are exceptions, having earned a less favorable reputation due to connecting rod and cylinder head issues in some production years. For any of the later diesel models, engine mount replacement is essential. For 1986 and 1987 300SD models sold in California, the original particulate filter should have been replaced with an oxidation catalyst if it hasn’t been already.
The S-Class, particularly models like the 500 SEC, became iconic symbols of the US gray market import phenomenon in the mid to late 1980s, before the Motor Vehicle Safety Compliance Act of 1988 curtailed this practice. While the 500SE and 500SEL were widely considered to be top-tier models from 1985 to 1991, Mercedes-Benz USA didn’t officially offer them in the US, and provided a limited selection of features and finishes. This led dealerships to bypass the official US sales network and import approximately 22,000 vehicles. The allure of models like the 1984 Mercedes 500 SEC, often with higher specifications and more luxurious options than officially available US models, fueled this gray market trend.
In conclusion, the 1984 Mercedes 500 SEC represents a high point in the W126 S-Class lineage. It embodies the luxury, performance, and engineering excellence that defined Mercedes-Benz in the 1980s. For enthusiasts and collectors today, a 1984 Mercedes 500 SEC remains a desirable classic coupe, offering a blend of timeless design, robust engineering, and a significant piece of automotive history.
