Mercedes-Benz W126

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Mercedes-Benz W126

Manufacturer	Mercedes-Benz
Production	1979–1991 (sedan) 1981-1991 (coupé)
Predecessor	Mercedes-Benz W116
Successor	Mercedes-Benz W140
Class	Full-size luxury car Grand tourer
Body style	2-door coupe 4-door sedan
Engine	Straight-5 3.0 L OM617 Diesel Straight-6 2.6 L M103 2.8 L M110 3.0 L M103 3.5 L OM603 Diesel V8 3.8 L M116 4.2 L M116 5.0 L M117 5.6 L M117
Wheelbase	2935 mm (280 SE)
Length	4995 mm (280 SE)
Width	1820 mm (280 SE)
Height	1430 mm (280 SE)
Curb weight	1560 kg (280 SE)
Similar	Saab 9000 Audi 200 BMW 7-Series Volvo 740

For a complete overview of all S-Class models see Mercedes-Benz S-Class.

The Mercedes-Benz W126, manufactured by the German automotive marque Mercedes-Benz premiered at the Frankfurt International Motor Show in September 1979. Initially both short (SE, SD) and long (SEL, SDL) wheelbase sedans were offered, but September 1981 saw the introduction of the coupé (SEC) body style. During the car's twelve year production run between 1979 and 1991 the different body styles achieved a combined sales of 892,123 units (818,063 sedans and 74,060 coupés), making the W126 the most popular S-Class to date.

1 History of development
2 Models produced
3 Technology and Features
4 Demand in the United States
5 Problem models
- 5.1 350 SD/SDL
- 5.2 380 SE/SEL
6 Popular Tuners and Variants
7 Engine model numbers
8 References
9 External links

[edit] History of development

The W126 replaced the 1970s generation W116 (including the flagship Mercedes-Benz 450SEL 6.9), and carried forward the self-leveling hydropneumatic suspension of the 6.9 as an option on the 500, and standard on the 560 models. Following the 1970s oil crisis, Mercedes-Benz made fuel efficiency a pertinent goal of the model, even in the large V8 engined models.

The car was introduced at the IAA in Frankfurt on September 1979. Its appearance differed from the rest of the Mercedes fleet at that time, so some people did not appreciate the design right away. The objective of the design team, lead by Bruno Sacco, was to produce a car that was sleeker, more aerodynamic, lighter and faster 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 and maximum speed was also increased.

Four years after the introduction of the energy concept, 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, already used in the new middle class W124 series, replaced the 2.8 litre DOHC M110 engines. The carburetted version was replaced by a 2.6 litre fuel injection engine. The 3.0 litre version replaced the fuel injected M110. New was the 4.2 litre V8 engine, designed to replace the 3.8 litre version used in the S-class limousine, the SEC and the SL. The 5 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.

The most spectacular 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. There was a higher compression version available, if required, that produced some 300 hp. 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.

The W126 generation was replaced by the W140 in 1992, although a satellite factory in South Africa is known to have continued production until 1994.

Early prototype displaying recognisable design cues from the W116

October 1975 prototype showing a strong resemblance to the W123 series

October 1975 prototype displaying design cues that would be seen latter on in the W140 S-Class

December 1975 prototype showing the basic overall shape of the production car

[edit] Models produced

Mercedes-Benz 560 SEC coupé

Rear-end of a 500 SEL W126

The W126 models (named in accordance to their engine size) included:

1979-1985:
- 280 SE/SEL (World excluding US)
- 300 SD ('81-'85, USA and Canada only)
- 380 SE/SEL/SEC
- 500 SE/(World excluding US)
- 500 SEL/SEC (for US and Canada '84 and '85)
1986-1991:
- 260 SE (World excluding US & Australia)
- 300 SE/SEL ('88-'91 US)
- 300 SDL ('86-'87)
- 350 SD/SDL ('90-'91)
- 420 SE/SEL/SEC
- 500 SE/SEL/SEC (World excluding US)
- 560 SE/SEL/SEC (560 SE n/a in US, Australia)

[edit] Technology and Features

W126 interior

Novel luxury features/options include:

Airbags, as an additional measure of occupant protection. The driver side airbag premiered on 1985 models (standard on 500 SEL and 500 SEC, optional on 300 SD, 380 SE, and 380 SL), and the passenger side airbag premiered in 1989.
Traction control ASR to prevent wheelspin (a Mercedes first). Available on European models only until the 1990 when it was available to 560 SEL customers in the United States.
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 brakes (as introduced by its predecessor, the W116)
Self-levelling suspension There were two versions for the sedan, a rear only hydraulic suspension using two nitrogen ballasts to automatically level the car, and a four-wheel hydraulic levelling system that could be set in three positions. The coupes were only available with the rear-levelling from the factory. In the US, rear-levelling was standard on both the 560 SEC and the 560 SEL.
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.
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.
Fully automatic climate control system that used an interior temperature sensor to more accurately climatize the cabin. This sensor was mounted near the sunroof so that when the roof was ajar, the sensor would detect cool windchills and call upon the system to adjust heat flow accordingly.
Exterior temperature sensor with display set in main instrument console below the speedometer to inform the driver of exterior conditions.
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.
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 plague many current cruise control systems.

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.

[edit] Demand in the United States

Gray-market Mercedes-Benz 500 SE

The 500 SEL has an interesting place in US 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. 25,000 units per year of the grey market vehicle were sold in the early 1980s, according to contemporary reports in the Los Angeles Times.

[edit] Problem models

[edit] 350 SD/SDL

Some engines had a design defect which causes ovaling of cylinders walls, bent rods, excessive oil consumption (1 quart per 200 miles or one litre per 300 kilometres is not uncommon), and eventually engine failure. Mercedes-Benz did not accept responsibility for this defect, even when problems arose before warranty terms were met. Most of these engine failures have so-far occurred on vehicles driven under high load or city driving, while highway driven engines do not show signs of problems until many miles later, if at all. Fixing the problem can cost the owner more than $10,000 or 8000€ which exceeds the value of the car. Not all 350 SD/SDL's have this issue, therefore a thorough pre-purchase check by a qualified mechanic can give the potential buyer a better idea of what they are getting into. Some 350's have gone well over 400,000 miles, problem free.

[edit] 380 SE/SEL

Following the fuel crisis, part of the programme was to reduce weight and increase power with decreased engine weight. On early versions of the 380, the engines came with a single row timing chain. These models were plagued with chain failure problems and some of the problems were corrected by Mercedes-Benz, free of charge. Some models, however, escaped retrofit and may at some point fail as a result. All models built in 1985 were equipped with the dual-row chain from the factory.

The reason for the susceptibility of a single row chain on this engine is because of the intricate rails and tensioner design, along with the two tall cam towers the chain must circulate around. Simple single cam engines generally do not have these problems when using a single chain

[edit] Popular Tuners and Variants

AMG, offered Bodykits for all W126 models, as well as a widebody kit for the coupe. 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 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, 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.