The Mercedes-Benz W126 is a series of flagship vehicles manufactured by German automotive marque Mercedes-Benz. Premiering in September 1979 as the successor to the earlier W116 line, the W126 was the second generation of the Mercedes-Benz flagship to officially bear the S-Class name referring to Sonderklasse or "special class." The W126 was initially offered in straight-6, V8, and turbo diesel sedan models. In September 1981, 2-door coupé versions of the W126 were introduced. Compared to its predecessor, the W126 was more aerodynamic, fuel efficient, capacious, and powerfully engined. The W126 S-Class debuted a new Mercedes-Benz design style which was subsequently used on other vehicles in the company's lineup. The W126 line also introduced many Mercedes-Benz safety innovations, including the first airbag supplemental restraint systems, seatbelt pretensioners, and traction control.
The W126 had a twelve-year production run between 1979 and 1991, the longest of any S-Class generation since the flagship models were first built in the mid-1950s.
Following the debut of the 1970s generation W116 (which also included the flagship 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. Following the 1970s oil crisis, 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.The maximum speed was also increased (250 km/h in the most powerful model).
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, SD) 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 (SEC) 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.
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 alloys, the 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 V8's 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.
In 1976, after several design concepts being presented, the design for the W126 S-Class was frozen. Design work on the coupe began immediately afterward. It premiered the next generation of Mercedes-Benz car styling, which came to dominate the lineup in the 1980s. Because the appearance differed from the rest of the Mercedes-Benz fleet at that time, some people did not appreciate the design at its debut. Compared to its predecessor, the W116, the new model had a sleeker, lower profile look, with more aerodynamic qualities than before (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.
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.
Novel luxury features/options included the following safety, comfort, and technological features. Whilst 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.
- Airbags, as an additional measure of occupant protection. The driver side airbag premiered on 1981 models, as an optional extra (standard from 1985 on 500 SEL and 500 SEC), and the passenger side airbag premiered in 1986 (as an optional extra; due to its expense, few early production W126 cars were thus equipped). The passenger side airbag became standard in 1989 for the 560 SEL and 560 SEC and was made standard in 1991 for all models.
- Traction control system (TCS), also known as Acceleration Slip Regulation (ASR) to prevent wheelspin (a Mercedes-Benz first). Available only on European models from 1989 until the model year 1991, when it was introduced on 560 SEL and SEC models in the United States for that last production year only.
- Seat belt pretensioners ETR enabled all seat belts (with exception of rear centre lap belt on sedans) to tighten when the car sensed conditions that could lead to an accident (such as sudden, forceful braking).
- Anti-lock braking system (ABS) (as introduced by its predecessor, the W116) was optional until 1986 except on premier 500 SEL and 500 SEC models.
- Crumple zones which absorbed impact energies, reducing passenger injury.
- Fluted taillights continuing the design pioneered on the W116, a design that helped maximise visibility of taillights from behind the car even when extremely dirty
- A third brakelight from 1986 on US-model cars, which provided a third brake lamp in the center of the rear windscreen as a safety feature. This change was mandated by US law for all foreign and domestic US-model cars as of the 1986 model year.
Comfort and convenience
- Courtesy lights on the underside of the doors, to enable the occupant to see the ground when exiting the vehicle in the dark. And on sedan models, individual, rear cabin reading lamps aimed at the rear-seat occupants' laps so as to avoid distracting the driver at night.
- Eight-way powered, dual stage heated front seats, with two setting memory functions for both front occupants to retain positions of power adjustable steering column and seat position for driver; and seat position for front passenger. The seat heaters were standard on the 560 SEL/SEC, and an option on other models. Later-production (post-facelift) models so equipped had higher wattage heated seats, as compared to earlier models.
- Two-way powered, dual stage heated rear "Chesterfield" bench seat (pre-1990 SELs) with four-way manually adjustable rear headrests that was standard on flagship 500 SEL and 560 SEL models.
- As an option on the 500 SEL and 560 SEL, individual, power adjustable rear seats were provided with a burl walnut grained centre console that replaced the centre seat to allow for a 2 + 2 seating format.
- A optional fully automatic climate control system that used an interior temperature sensor to more accurately climatize the cabin. This sensor was mounted overhead (near the sunroof switch) so that when the roof was open, the sensor would detect cool air-flow and call upon the system to adjust heat flow accordingly.
- Exterior temperature sensor with LCD display set in main instrument console below the speedometer to inform the driver of exterior conditions. This was delineated in Fahrenheit for US-market cars, and in Celsius for the rest of the world.
- Four-speed automatic transmission with a topographical sensor that monitored the vehicle's position (whether on an incline or decline) and gas pedal position. The result was an extraordinary capacity to "hold back" acceleration when coasting downhill and to maintain the S-Class' position without using the brake pedal after coming to a complete stop on a steep incline. The transmission also featured a "limp home mode" in case of electronic failure and was programmed to start in second gear so as to permit smooth, wheel spin free launches. Second gear start could be switched on and off in European models with a S/W switch to allow more performance orientated driving versus winter driving.
- The W126 carried forward the self-leveling hydropneumatic suspension of the W116 450 SEL 6.9 model. There were two versions of the self-leveling suspension for the sedan: a rear only hydraulic suspension using two nitrogen ballasts to automatically level the car, and a four-wheel hydraulic leveling system that could be set in three positions. The coupés were only available with the rear-leveling from the factory. In the US, rear-leveling was standard on both the 560 SEC and the 560 SEL, and optional on the 500 SEC and SEL. The four-wheel hydraulic leveling system was never made available for North American-market cars.
- Cruise control that used the transmission's topographical sensor to appropriately add and cut back the throttle fluidly as needed in order to maintain the desired set speed. The result was a cruise control that was free of the sudden throttle inputs and undesired downhill excess speed that plagued many contemporary cruise control systems.
In September 1985, two newly constructed six-cylinder SOHC engines, M103 (already used in the new middle-class 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 and electronic-mechanical fuel injection in form of the Bosch KE-jetronic system. 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 engine was the 5.6-litre V8 that was a further development from the 5 litre version. An increased stroke meant it could turn out a hefty 272 hp (203 kW). There was a higher compression version available, if required, that produced 300 hp (220 kW). 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 DPF. 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.
- AMG offered body kits for all W126 models, as well as a widebody kit for the coupé. AMG also offered many levels of engine tuning, but was most famous for the DOHC 6.0 litre engine, based on the original 117.968 engine. Also offered was a Gleason Torsen differential in varying ratios, manual transmission (extremely rare), and various TV/radio consoles.
- Brabus Offered body kits similar to the AMG package and engine tuning.
- Lorinser Offered body kits similar to the AMG package and minor engine tuning.
- Koenig Specials offered a famous widebody kit, a supercharger, and twin-turbo kits.
- MKB offered various engine kits
- RennTech offered most of the AMG engine tuning packages except for the DOHC engine.
- Carat-body kits, wooden seatback trays, wood trim, AMG installer/dealer.
- Transco Bremen offered a stretch limousine version called the "1000 SEL".
Like the current model S-Guard, specially modified W126 S-Class models were produced for the transport of diginitaries and world leaders. Among the modifications made included a wheelbase stretch, bulletproof glass, and armored body panels.
U.S. grey market
The 500 SEL has an interesting place in U.S. automotive history, since American demand for this particular car drove the establishment of a large grey market. The detuned, yet very expensive US specification 380 SE/SEL/SEC was underpowered, according to contemporary reports, and fuelled demand for the more powerful version available in the rest of the world. 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 other had issues with the rear axle.
The W126 S-Class was a champion in the luxury car market, dominating worldwide sales during its production run. At the same time, it also achieved several awards during its production period. 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.
The W126 S-Class, the most successful production S-Class in history, has secured a place as one of the most well-remembered luxury vehicles–described by some as a "classic." Its twelve-year production run was longer than any S-Class before or since, and following the debut of the W140 S-Class in 1991, the additional two years of production in South Africa was a testament to the W126's popularity in the export market. Although an expensive car to maintain, mostly due to the increased expense of Mercedes-Benz replacement parts, a late model W126, if properly driven, can still be a viable proposition today. Many W126s have been prominently featured in films long after production ended.
This legacy stands in contrast with the W140 chassis which had very complex accessory systems, particularly the W140 HVAC system, electrical wiring (due to the push to manufacture environmentally friendly plastics), and auto-door closing features. Among actual owners, W126s are known for their simple maintenance, straightforward problems diagnosis, and long term reliability.