The Mercedes-Benz W126 is a series of S-Class automobiles manufactured by Mercedes-Benz between 1979 and 1992. Premiering in September 1979 as the successor to the W116 line, the W126 was the second generation to officially bear that prestigious designation, an abbreviation for the German Sonderklasse or "special class." It introduced many Mercedes-Benz safety innovations, including the first seatbelt pretensioners.
The W126 was initially offered with straight-six, V8, and a turbocharged diesel engine for the sedan. A C126 2-door coupé versions was introduced in September 1981.
The W126's twelve-year production run between 1979 and 1991 was the longest of any S-Class generation since the first "S" designated top-class models were built in the mid-1950s, the 300 S and 300 Sc.
Following the debut of the 1970s generation W116 (which also included the limited-production Mercedes-Benz 450SEL 6.9), Mercedes-Benz began plans for the next-generation S-Class model in October 1973. Codenamed "project W126," the project had specific goals: an improved ride, better handling, and improved fuel efficiency. These improvements were aimed at helping retain the S-Class' market leadership as the world's best-selling prestige luxury sedan. Mercedes-Benz had made fuel efficiency an especially pertinent goal (named "Energy Program"), even in the large V8 engined versions of the S-Class.
In terms of the body design, the objective of the W126 design team, led by Mercedes-Benz's Bruno Sacco, was to produce a car that was sleeker and more aerodynamic than the previous model. The application of lighter materials and alloys combined with thorough wind tunnel testing to reduce overall drag meant the car consumed about 10% less fuel than its predecessor.
After six years of development, the W126 was formally introduced at the Internationale Automobil-Ausstellung (International Motor Show, or IAA) in Frankfurt on September 1979. The initial lineup featured seven models in standard (SE S-Klasse-Einspritzmotor, SD S-Klasse-Diesel) and long (SEL, SDL) wheelbase sedan body styles: the 280 SE/SEL, 380 SE/SEL, 500 SE/SEL and 300 SD. Technically, the long-wheelbase (SEL) variants were codenamed V126, but this was not popularly known. In 1981, the coupé version C126 (SEC, acronym for (German) S-Klasse-Einspritzmotor-Coupé) of the W126 S-Class premiered at the IAA with the 500 SEC model. In 1981, Wheels Magazine selected the W126 model 380 SE as its Car of the Year.
Although the top of range Mercedes-Benz 450SEL 6.9 of the previous generation was not directly replaced, the W126 carried forward the hydropneumatic suspension of the 6.9 as an option on the 500SEL and later on 420SEL and 560SEL models.
Four years after the introduction of the fuel-efficiency "Energy Program," the model range had been reworked completely. In September 1985, again at the IAA in Frankfurt, the reworked model range was reintroduced. Apart from visual changes to the bumpers, side covers and larger 15 inch wheels with a new design on the hubcaps and alloys (optional), there where a number of technical upgrades as well as changes made to the available collection of engine variants was most visible. Two newly constructed 6-cylinder engines and new 4.2- and 5.6-litre V8s were added, and other engines were further upgraded.
The W126 generation was replaced by the W140 in 1991, although a satellite factory in South Africa is known to have continued production until 1994. The different body styles of the W126 S-Class achieved a combined sales total of 892,123 units (818,063 sedans and 74,060 coupés), making the W126 the most popular S-Class ever produced.
From 1973 to 1975, Mercedes-Benz designers worked on the successor to the W116. In December 1975, after several design concepts being presented, the design for the W126 S-Class was approved and frozen in 1976. Design work on the coupe began immediately afterward, being finalized in 1977. It premiered the next generation of Mercedes-Benz car styling, which came to dominate the lineup in the 1980s. Compared to its predecessor, the W116, the new model had more aerodynamic qualities than before (with a drag coefficient of Cd 0.36 for the sedans, 0.34 for the coupés). For the first time, a Mercedes-Benz sedan was not equipped with traditional chrome bumpers; polyurethane deformable bumpers were used, and visually aligned with body panels. Design patents were first filed on March 3, 1977 and later on September 6, 1977 at the United States Patent Office.
The interior featured pleated leather on the doors on later cars and woodgrain trim on the center console and across the dash, and a simplified layout with symmetrically placed buttons. Both zebrano and burled walnut were used on low/mid and high-end cars, respectively.
In 1985, Mercedes-Benz issued a facelift for the 126 series cars; revised bumpers, body side protection mouldings, and wheel designs differentiated the updated models.
The W126 series (named in accordance to their engine size) initially included the 280, 300, 380, and 500 series models. Following the first S-Class mid-cycle refresh, the W126 series included 260, 300, 350, 420, 500, and 560 models. Variants included SE (standard wheelbase), SEL (long-wheelbase), SEC (coupé), and diesel models (SD and SDL).
Novel luxury features/options included the following safety, comfort, and technological features. While almost all of these features are available on modern luxury cars today, each in its own right was considered very significant in the 1980s. The harmonious and "matter-of-fact" way which these were combined, as well as their renowned durability, has added to the appeal of W126.
In September 1985, two newly constructed SOHC 2 valves per cylinder inline-six engines, M103 (already used in the new mid-sized Mercedes-Benz W124 series), replaced the 2.8-litre DOHC M110 engines. The carburetted version was replaced by a 2.6-litre fuel injection engine, while the 3.0-litre version replaced the fuel injected M110. Also new was a 4.2-litre V8 engine, designed to replace the 3.8-litre version used in the W126 sedans, coupés, and the SL-Class. The 5.0-litre engine was modified to receive electronic ignition system and in form of the Bosch KE-jetronic electronic-mechanical fuel injection. Performance was increased to 245 hp (183 kW). An ECE version of the 5.0-litre M117 V8 engine was also available from September 1987 with a power output of 265 hp (198 kW)
The largest new V8 engine was the 5.5 L (5,547 cc) that was a further development from the 5-litre version. An increased stroke of 94.8 mm (3.73 in) resulted in an increased peak power output of 272 hp (203 kW). There was a higher compression ratio of 10:1 version available, if required, that produced 300 PS (296 bhp; 221 kW) at 5000 rpm and 455 N⋅m (336 lbf⋅ft) at 3750 rpm of torque. This version was only available without catalytic converter. But even without the catalytic converter this ECE version, as it was known, would meet the emission requirements of the European community.
A 3.0-litre inline-five cylinder turbo diesel was offered from 1981–1985 in North America. In 1986, the 300SD was replaced with the 300SDL. It was part of the second generation of W126 model lineup. The five-cylinder engine was replaced with the new inline six-cylinder engine and the engine was only offered in long-wheelbase. The new engine had 148 hp (110 kW) compared to 125 hp (93 kW) of the previous version. California specification 1986 and all 1987 cars were the first diesel cars to have a diesel particulate filter. This early implementation did not hold up under normal use, and was replaced by a standard diesel oxidization catalyst in the course of a recall.
The 500 SEL has an interesting place in U.S. automotive history, since American demand for this particular car was high, it drove the establishment of a large grey market. The 380 SE/SEL/SEC was perceived as underpowered by American standards, according to contemporary reports, thus driving up demand for the more powerful version that was the 500. Approximately 22,000 units per year of grey market Mercedes-Benz (including the 500 SE/SEL) were sold in the early 1980s, according to contemporary reports in the Los Angeles Times.
Two AMG-modified 500 SEC cars raced at the 1989 24 Hours of Spa. Both cars failed to finish, with one suffering gearbox issues, while the other had issues with the rear axle.
The W126 S-Class achieved several awards during its production period. The W126 model 300 SD was the Motor Trend Import Car of the Year in 1981. The W126 model 380 SE was the Wheels Magazine Car of the Year in 1981, the W126 was awarded the U.S. Highway Loss Data Institute "Safest Passenger Car of the Year" in 1988 and 1989, and the W126 was the third-ranked luxury vehicle in J.D. Power's 1990 Initial Quality Survey (IQS). In 1987, 1988, 1989, and 1990, with the W126 S-Class leading its sales, Mercedes-Benz received the highest customer ratings in the J.D. Power Sales Satisfaction Index.
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