Mercedes-Benz W108/W109

Model history

Chassis (platform)

The car's predecessors, the W 111 (1959–71) and W 112 (1961–67), helped Mercedes-Benz develop better sales and achieve economy of scale production, reducing both manufacture time and cost. Throughout the 1950s, Mercedes-Benz had been producing the coachwork 300 S and 300 SL and all but hand-built 300 "Adenauer" (W 189) alongside conveyor assembled Pontons (190, 190 SL and 220) etc. Unifying the entire Mercedes-Benz range into the "fintail" () reduced production onto a single automobile platform.

Body design

Fashion trends in the early 1960s changed rapidly. By the time the Paul Bracq-designed 2-door coupé and cabriolet W 111 were launched, the predecessor W 111 sedan's fins lost their chrome trim and sharp appearance. The arrival of the W 113 'Pagoda' coupé and cabriolet in 1963 saw them further buried into the trunk's contour. Finally, they disappeared completely on the 600 (W 100) in 1963.

The evolution of the W 108 began under the leadership of Bracq in 1961 and ended in 1963. Although the fins' departure was the most visible change, the W 108 had a lower body waist line and increased glass area – the windscreen alone was 17% larger than W 111's – prominent enough to be referred to as a "greenhouse". The cars had a 60 mm lower ride and 15 mm wider doors. The result was a visibly newer-looking, sleeker car with an open and spacious interior.

Differences between W 108 and W 109

Originally, the W 108 was seen as a combined successor to the W 111 and the short wheelbase sedans in the W 112 line lacking air suspension.

The W 111 had been a successor to the six-cylinder Ponton models of the mid 1950s; the W 112 derived from it was a stopgap to replace the hand-built body-on-frame 300 "Adenauer" (W 189) state car (built through the spring of 1962) pending the 1963 introduction of the 600 "Grand Mercedes" (W 100; ). In addition to being lavishly decorated with additional chrome trim, the W 112 inherited the alloy block M 189 engine of the W 189, and featured a self-levelling air suspension. A long-wheelbase version was offered from March 1963 through July 1965.

This introduction of two lines (standard and luxury) emerged the W 108 and W 109 models, with the dividing line running between luxury, performance and air suspension. Thus that expensive feature was kept on the long wheelbase W 109 300 SEL, while models from the 300 SEb down retained their steel coil springs and oil-filled shock absorbers.

1965: 250 and 300 series

The initial 1965 product line was the W 108 series' 250 S, 250 SE, and 300 SEb, and only the 300 SEL produced as a W 109. As before, the 300 series were more luxuriously appointed than the 250 series, featuring burled walnut dashboards and power windows along with optional automatic transmission and air conditioning. The W 109 also featured door window frames and a-pillars fully finished with polished metal bright trim.

1968: 280 and 300 series

In 1968 Mercedes-Benz retired the M189 engine in favor of the new 2.8L M130. As a result, the long wheelbase W108 280 SEL and W109 300 SEL (which shared a 2850 mm wheelbase) also ended up sharing the 2.8L engine through the end of production in 1972. Similarly, the M116 V8 powered W108 280 SE/SEL 3.5 and W109 300 SEL 3.5, and the M117 V8 powered W108 280 SE/SEL 4.5 and W109 300 SEL 4.5, shared wheelbases and engines through the end of production in 1972.

Mercedes-Benz refused to name these models 350 SEL and 450 SEL to avoid upsetting the release of the W116 S-Class.

First Series (1965–1967)

Market introduction

The W 108/W 109 premiered at the Frankfurt Auto Show in 1965. The initial model range consisted of three W 108s (250 S, 250 SE, and 300 SEb) and a sole W 109 (300 SEL). The inline-six engines were carried over from the previous generation with mechanical refinements. The 2.2 L M 180 engine was enlarged to 2.5 L while the fuel-injected 3.0 L M 189 version was carried over from 300 "Adenauer".

250 series

The 250 S was fitted with 2497 cc M 108 engine with 2 compound downdraft carburetors producing 130 PS at 5,400/min. The 250 SE had the same engine as 250 S except for fuel injection system and different engine designation (M 129) with increased engine output of 150 PS at 5,500/min.

300 series

Both 300 SEb and 300 SEL were fitted with 2996 cc M 189 engine. The engine was an updated version of M 186, originally developed in 1951 for the 300 "Adenauer", with Bosch 6-point mechanical fuel injection system that calibrated the optimal fuel mixture automatically based on throttle pedal position and movement, engine speed, atmospheric pressure, water temperature, and driving conditions. The engine's output was 170 PS at 5,400/min.

Production figures

The production figures for the first series from 1965 to 1967 showed 129,858 of 250 S/250 SE and 5,106 of 300 SEb/300 SEL. The tiny production figure of 300 SEb/300 SEL reflected the higher sales price with luxurious appointments, exclusivity, and smaller global market share.

300 SEL 6.3

Main article: Mercedes-Benz 300 SEL 6.3

In 1966, company engineer Erich Waxenberger transplanted a massive 6333 cc M 100 V8 from the company's flagship 600 (W 100) with 250 PS at moderate 4,000/min and 51 kpm at 2,800/min for superior power delivery into a W 109 chassis, creating the first Q-car from Mercedes-Benz. Full-scale production of 300 SEL 6.3 began in December 1967. 300 SEL 6.3 could reach 100 km/h in 6.5 seconds and the top speed of 221 km/h, making it the quickest production sedan, a title it held for many years.

Second Series (1967–1972)

Market introduction

To coincide with the launch of new cheaper executive, W 114/W 115 "/8" (Stroke Eight); ) models, slotted below MB's W 108 and W 109, the inline six engine range was revised in 1967. The 2.5 L engine was enlarged to 2778 cc and renamed as M 130 for both carburetted 140 PS at 5,200/min and fuel injected 160 PS at 5,500/min versions.

2.8 L I6 models

250 S and 250 SE were renamed as 280 S and 280 SE in November 1967 while 250 S was still offered in some export markets until March 1969. In January 1968, a long wheelbase variation, 280 SEL, was introduced for the first time.

The standard wheelbase 300 SEb was dropped while 300 SEL 2.8 obtained the 2.8 L engine with higher output 170 PS at 5,750/min, replacing the M189 engine.

3.5 L V8 models

Following the strong reception of the limited production 6333 cc M 100 V8-powered 300 SEL 6.3 in 1967, Mercedes-Benz offered the all-new 3.5 L M 116 V8 engine with new Bosch D-Jetronic electronic fuel injection in 1969. The V8 engine would move W 108/W 109 further upmarket in many export markets and allow them to be more competitive in the United States where many passenger vehicles, especially the American luxury marques, were fitted with V8 engines. The new 200 PS at 5,800/min V8 engine was first fitted to W 109 in August 1969 as 300 SEL 3.5 then to W 108 in July 1970 as 280 SE/SEL 3.5.

4.5 L V8 models

With a different crankshaft the 3499 cc V8 engine was enlarged to 4520 cc as to compensate for the loss of power following the changes in emission control regulations and due to lower fuel octane rating in the United States while increase torque for the use with a three-speed automatic with torque converter to suit the US market. The 4.5 L V8 engine was designated as M 117 and had with 195 hp almost the same power as the domestic 3.5 L V8 engine. It was initially exclusive for the United States, introduced in the spring of 1971, as the 280 SE/SEL 4.5 and the 300 SEL 4.5, until the new, 1973 model year W 116, MB's first generation of distinct S-Class platform 450 SE/SEL models, which went on sale worldwide in September 1972, alongside the V8 powered 350/450 SL (R 107) 2-seat cabrios and the 350/450 SLC (C 107) 4-seat luxury coupes.

Production figures

The production figures for the second series from 1967 to 1972 showed 184,717 of 280 S/280 SE and 10,769 of 280 SEL/300 SEL. 52,622 units sold with V8 engine reflect that it was right to switch to V8 engines in the luxury car segment.

Discontinuation

The 300 SEL 2.8 was dropped in January 1970 since the 300 SEL 3.5 was selling better and had better performance. The production of 280 SEL ended in April 1971, leaving 280 S and 280 SE as sole models with six-cylinder inline engines until the end of W 108/W 109 production in 1972, following the introduction of W 116.

Transmission

In-house developing and production

Unusual among mainstream European automakers of the time, Mercedes developed and built their own automatic transmission system, first went into production in 1961.

I6 models

The standard transmission for Europe was a four-speed manual gearbox. As an option a four-speed automatic with fluid coupling was available. For the first series it was the K4A 025; for the second series the more reliable and smoother shifting all new K4C 025 was introduced in May 1969. A five-speed manual gearbox was offered for six-cylinder 2.8 L and 3.0 L engines, though a few customers opted for it.

Big block V8 model

As a pilot the first model of the more reliable and smoother shifting all new four-speed automatic with fluid coupling layout was the K4B 050, 1963 introduced for the 600 and later the 300 SEL 6.3 respectively. Beside the new layout the number of pinions is doubled from 3 to 6 to handle the much higher torque of the big block V8 engine M 100.

In-house automatic transmission family

After the satisfactory experience with the new design, it was adopted for the new core model K4C 025 for 4- to 6-cylinder engines. With the small block V8 engine M 116, the K4A 040 was launched as a reinforced version of the same design. With the small block V8 engine for the United States M 117, the three-speed automatic with torque converter W4A 040 was derived from this design. It was the first automatic with torque converter Mercedes-Benz offered.

Small block V8 models

When the 3.5 L V8 engine was introduced in 1969, the sole transmission choice was the K4A 040. Customers could request the four-speed manual transmission with price reduction if they inclined so. For 4.5 L V8 engine for the United States, the sole transmission choice was the W3A 040.

Models

Timeline

Technical info

References

Notes

Bibliography

General

Workshop manuals

References

1. Koehling, Bernd S.. "Mercedes 250S, SE W108: Mercedes elegance at its best".
2. (March 13, 1967). "X-ray of Mercedes-Benz 250S fails to find an ounce of fat.". Eugene Register-Guard.
3. (2 February 1967). "Autocar Road Test: Mercedes-Benz 250 SE". [[Autocar (magazine).
4. Covello, Mike. (2002). "Standard Catalog of Imported Cars 1946-2002". Krause Publication.