Mercedes-Benz W108/W109

Mercedes-Benz W 108 • W 109
Overview
Manufacturer	Daimler-Benz
Production	1965–1972 383,072 built W 108: 359,522 W 109: 23,550[1][2]
Assembly	West Germany: Stuttgart
Designer	Paul Bracq, Friedrich Geiger (1963)
Body and chassis
Class	Full-size luxury car (F)
Body style	4-door sedan
Layout	FR layout
Related	W113 W111/W112 (2 door models)
Powertrain
Engine	2.5 L I6 M 108 & M 129 2.8 L I6 M 130 3.0 L I6 M 189 3.5 L V8 M 116 4.5 L V8 M 117 6.3 L V8 M 100
Transmission	4-speed manual 5-speed manual 4-speed automatic K4A 025 K4B 050 K4C 025 K4A 040 3-speed automatic W3A 040
Chronology
Predecessor	W 108: W 111 W 109: W 112
Successor	W 116

The Mercedes-Benz W 108 and W 109 are luxury cars produced by Mercedes-Benz from 1965 through to 1972. They succeeded the W 111 and W 112 "fintail" (German: "Heckflosse") sedans, and upon their introduction, the manufacturer designated them as constituting a newly created "Upper Middle Class" range. The cars were successful in West Germany and in export markets including North America and Southeast Asia. During the seven-year run, a total of 383,072 units were manufactured.^[2]

As the W 108 and W 109 were only available as 4-door models, the similarly squarish, Paul Bracq-designed 2-door W 111 and W 112 coupés and cabriolets filled those niches and are frequently mistaken for W 108/W 109 two-doors. The range was complemented by the sophisticated 300 SEL, as well as the 300 SE Coupé and Cabriolet variants, which continued the renowned 300 series lineage in a modern form.

Mercedes-Benz W 108 280 SE

As the W 108 and W 109 were only available as 4-door models, similarly squarish Bracq-designed 2-door W 111 and W 112 coupés and cabriolets, like this 1969 280 SE, are frequently mistaken for them.

The car's predecessors, the W 111 (1959–71) and W 112 (1961–67), had helped Mercedes-Benz develop better sales and achieve economy of scale production by unifying the entire Mercedes-Benz range onto a single automobile platform, reducing both manufacture time and cost. The evolution of the W 108 body began under the leadership of Paul Bracq in 1961 and ended in 1963. The development was governed by a strict hierarchy of functional considerations over stylistic or fashionable trends, a decades-long practice at Daimler-Benz. The primary goal was to increase the passenger compartment while maintaining the favorable exterior dimensions of the previous six-cylinder models, simultaneously achieving particularly high levels of driving safety, ride comfort, and performance.^[3]

While the external dimensions were only marginally increased relative to the preceding Type 220 S—specifically, an increase in length of 25 mm (1.0 in), an increase in width of 15 mm (0.6 in), and a reduction in height of 60 mm (2.4 in)—the utilization of interior space was radically improved. This was achieved primarily through the adoption of curved side windows and a lowered beltline. The interior width consequently increased by 70 mm (2.8 in) in the rear seating area and by 90 mm (3.5 in) in the front seating area. Furthermore, the floor in front of the rear seats was lowered by 20 mm (0.8 in), resulting in increased footwell space. The elongated, low silhouette served the primary engineering purpose of lowering the vehicle's centre of gravity, a factor cited as being of particular importance for good road holding. Although the fins' departure was the most visible change, the lowered beltline facilitated larger window areas; the windscreen alone was 17 percent larger than that of the W 111, with total glass area increasing by 12 percent, prominent enough to be referred to as a "greenhouse." The result was a visibly newer-looking, sleeker car with an open and spacious interior.^[4] The flat roof and smooth rear end treatment were noted as being stylistically reminiscent of the Mercedes-Benz coupés, whose sporty and elegant design had garnered worldwide acclaim. The front aspect featured the traditional Mercedes-Benz radiator grille with a wide opening and lowered hood, flanked by vertically arranged lighting units that combined the functions of high beam, low beam, parking lights, fog lights, and turn signals into a single, integrated assembly.

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 pending the 1963 introduction of the 600 "Grand Mercedes" (W 100; German: "Grosser Mercedes"). 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.

The 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, the expensive self-levelling air suspension feature was kept on the long-wheelbase W 109 300 SEL, while models from the 300 SEb down retained their steel coil springs and a newly developed hydropneumatic compensating spring on the rear axle. This device functioned to maintain a nearly constant ride height at the rear, largely independent of load, thereby preventing the rear end from sagging even under heavy cargo weight. As before, the 300 series were more luxuriously appointed than the 250 series, featuring burled walnut dashboards, power windows, and fine wood trim with premium upholstery fabrics and leather, 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. Standard comfort and convenience features across the entire range included individual front seats with three-way adjustment (longitudinal, vertical height, and continuously variable backrest angle), a powerful heating and ventilation system with a continuously variable fan and dust filter, continuous ventilation outlets beneath the rear window to prevent fogging, and a comprehensive lighting package including trunk, glove compartment, and headlight flasher. Among the extensive range of optional extras available across the range were an electrically operated sunroof, electric window lifts, DB power steering, and a sporty centre-mounted shifter for the standard fully synchronised manual transmission.

In the design of the new body, the latest findings regarding internal and external occupant protection, based on intensive accident research conducted by Daimler-Benz AG, were incorporated. The structure adhered to the principle of a robust passenger safety cell combined with impact-absorbing crumple zones. The passenger compartment itself was engineered to be exceptionally robust and rigid, while the front and rear sections were designed to be relatively easily deformable to mitigate impact energy.

Internally, a comprehensive suite of passive safety measures was standardised across all models. The instrument panel was embedded within a shock-absorbing frame, and the steering wheel was equipped with a safety hub featuring a large, padded plate. The dashboard was effectively padded along both its top and bottom edges. All pull knobs and door handles were fabricated from elastic materials, and the doors were fitted with special safety locks designed to prevent them from springing open under any circumstances. For exterior protection against minor parking damage, rubber protective strips were integrated into the bumpers, and plastic strips were incorporated into the side trim mouldings.

All models were equipped as standard with a dual-circuit power braking system and disc brakes on all four wheels, a configuration deemed fully capable of handling the high speeds of which the vehicles were capable. The parking brake was configured as a small auxiliary drum brake integrated within the hub of the rear brake discs. A novel component, identified as a brake force regulating valve, was installed in the hydraulic circuit serving the rear wheels. During light deceleration, it allowed for the use of larger wheel cylinders on the rear brakes, engaging the rear wheels more extensively for improved stability; during heavy braking, it prevented overbraking at the rear axle, thereby inhibiting wheel lock.

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 significant mechanical refinements. The 2.3 L M 127 engine was stroked to 2.5 L while the alloy-block 3.0 L M 189 version was carried over from the W112.

The models were complemented by the W111 250SE coupe and cabriolets, which got the stroked M129 motor, and the W112 300SE which retained the M189 engine.

It is important to note that whilst the W108 and W109 are seen as successors to the W111 sedans, they did not replace them. The W111 230S model would be produced along the first series, among the newly organised 200/200D and 230/230S series.

The 250 S^[5] was fitted with a 2,497 cc (152.4 cu in) M 108 engine with 2 compound downdraft carburetors. A significant engineering advancement was the adoption of a seven-bearing design for the crankshaft, wherein a bearing was positioned before and after each crank throw. This resulted in a crankshaft of considerably greater stiffness and smoother operation, capable of sustaining a maximum engine speed of 6,300 revolutions per minute. The compression ratio was increased, and the cylinder head received enlarged intake and exhaust ports and valves. Cooling was managed by a standard-fit oil cooler and a viscous fan clutch, a coupling designed to engage automatically only when particularly large amounts of heat required dissipation, thereby saving engine power and reducing noise under normal operating conditions. Electrical supply was provided by a three-phase alternator fitted as standard, capable of supplying power to all consumers and charging the battery even at idle. The engine produced 130 PS (96 kW; 128 bhp) at 5,400 rpm. Top speed was approximately 180 km/h (112 mph).

The 250 SE had the same engine as the 250 S except for a mechanical fuel injection system utilising a six-plunger injection pump, and a different engine designation (M 129). The increased engine output was 150 PS (110 kW; 148 bhp) at 5,500 rpm. The 250 SE was further distinguished by a standard dual exhaust system. Top speed was 190 km/h (118 mph).

Visually the tell-tale feature of all W109 models was the thick chrome strip on the window frames (below) that would be absent on all W108 models irrespective of engine, wheelbase or model name.The top example is a 250SE. Vertically paired headlights was originally a feature of all US-exported models to comply with the DoT regulations on sealed beam headlights. However, these were introduced on European markets on selected V8 models later in the production.

Both the 300 SEb (standard wheelbase) and 300 SEL (long wheelbase, W 109) were fitted with the 2,996 cc (182.8 cu in) light-alloy M 189 engine. This engine was an updated version of the M 186, originally developed for the 300 "Adenauer," with a 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 (125 kW; 168 bhp) at 5,400 rpm (DIN), with maximum torque rated at 25.4 kp⋅m (249 N⋅m; 184 lb⋅ft) at 4,000 rpm. With the standard rear axle ratio of 1:3.92 and automatic transmission, top speed was approximately 185 km/h (115 mph); with the optionally available "faster" rear axle ratio of 1:3.69 in conjunction with the mechanical transmission, a top speed of approximately 200 km/h (124 mph) was attainable.

Crucially, the mechanical specifications of the 300 SEL diverged fundamentally from the 300 SEb. Whereas the outgoing W112 300 SE and 300 SE long models had previously been identical in their mechanical components, this approach was abandoned for the new generation. The W 109 300 SEL, with its longer chassis, occupied a prominent and distinct position within the range, defined by a set of mandatory, sophisticated mechanical components. While the 300 SEb retained the steel spring and hydropneumatic compensating spring configuration, the 300 SEL was equipped as standard with Daimler-Benz air suspension. This system, developed in cooperation with Phoenix for the rubber rolling bellows and Bosch for the regulating valves, provided automatic levelling, ensuring ground clearance and suspension travel remained constant regardless of vehicle load. As the full compression length was always available, the air suspension could be tuned to a softer rate than was feasible with conventional steel springs, allowing for optimal adjustment of toe and camber and resulting in improved road holding characteristics. This divergence in suspension specification created a price advantage for the 300 SEb relative to the more complex 300 SEL. The 300 SEL was further distinguished by mandatory DB power steering and the DB four-speed automatic transmission. A fully synchronised four-speed manual transmission was available as a price-reducing option. An optional limited-slip differential was also available for the 300 SEL to facilitate the effective transfer of the engine's high power output to the road surface even under adverse traction conditions.

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 very small production figure of 300 series reflected the higher sales price with luxurious appointments, exclusivity, and smaller global market share.

The 300 SEL 6.3 was a high-performance variant of the W 109, created in 1966 when company engineer Erich Waxenberger transplanted the 6,333 cc (386.5 cu in) M 100 V8 from the flagship 600 (W 100) into the W 109 chassis. Intended to bridge the gap between the existing 300 SEL and the 600, the result was the first Q-car from Mercedes-Benz. Full-scale production began in December 1967, and the model was formally presented at the Geneva Motor Show on 14 March 1968, and subsequently at the British International Motor Show in October 1968 in London.

Daimler-Benz positioned the 300 SEL 6.3 as a temperamental long-distance limousine combining optimal comfort with superb driving performance. The company acknowledged that the sole criticism of the existing 300 SEL had been a desire among a select group of customers for even greater speed; the superiority of the air-suspended chassis had the effect of making very fast driving feel comparatively sedate. The significance of the new model lay less in its absolute top speed and more in its exceptional acceleration. The 300 SEL 6.3 could reach 100 km/h (62 mph) from standstill in 6.5 seconds and cover 1 km (0.6 mi) from a standing start in 27.1 seconds. The power-to-weight ratio was 6.95 kg/HP (DIN), or 5.8 kg/HP (SAE, 12.8 lbs/HP), equal to that of high-performance sports cars. Top speed was approximately 220 km/h (137 mph), with a reported maximum of 221 km/h (137 mph). Fuel consumption varied between 14 and 24 litres per 100 kilometres, with a fuel tank capacity of 105 L (27.7 US gal; 23.1 imp gal) including a 14-litre reserve.

The M 100 V8 engine, carried over from the 600 with only a few modifications, delivered 250 PS (184 kW; 247 hp) (DIN) at 4,000 rpm and 300 hp (224 kW; 304 PS) (SAE) at 4,100 rpm, with maximum torque of 51 kp⋅m (500 N⋅m; 369 lb⋅ft) at 2,800 rpm. The fuel injection system employed an eight-plunger injection pump with an automatic starting and warm-up unit, injecting fuel into the induction pipe via eight jets at a pressure of 213 psi (15 kg/cm²). The standard four-speed automatic transmission with hydraulic clutch and three planetary gear sets was carried over from the 600. The rear axle was modified with a final drive ratio of 2.85.The braking system was enhanced with internally ventilated disc brakes on all four wheels, and the power steering required only slightly more than 2.5 turns from lock to lock. Super-low profile radial-ply tyres of size FR 70 VR 14 (205 VR 14 L) with tubes were fitted as standard.

The bodywork differed from the standard 300 SEL only in external details: the lettering "6.3" on the right side of the boot lid and three halogen double headlamps in which the dipped and high-beam units were designed as a single assembly, providing longer range and consistent brightness. The headlamp frame design was derived from the US-specification versions originally developed for sealed beam lenses. These headlamps were, initially, exclusive to the 6.3. The interior featured a speedometer with an extended range, a standard-fit revolution counter, and a newly located clock. Standard luxury equipment included a vacuum-controlled central locking system, electrically operated side windows, and illuminated boot, glove compartment, ashtray, cigar lighter, and heater levers. An air conditioning system was available as an option.

A total of 6,526 units were produced before the model was discontinued in September 1972. In the assessment of its manufacturer, the combination of the M 100 engine, automatic transmission, and air suspension gave the 300 SEL 6.3 a position on the international automobile market that was matched by no other automobile.^[6][7]

In 1968, at the Brussels Motor Show in January for Europe and the Chicago Auto Show in February for the United States^[8] Mercedes-Benz unveiled its new executive W 114/W 115 "/8" (Stroke Eight); German: "Strich-Acht") models. Also designed by Paul Bracq, they closely mimicked the W108 and W109 models, completing the transition to this corporate style, which began with the two door W111 models in 1961.^[9] Mechanically they rode on chassis and platform of a clean-sheet design, and were slotted below the W108 and W109 models to replace the now archaic W110 and W111 Fintail sedans, labelled as the medium-class in official press-releases ^[7]. Mercedes-Benz would embark on development of the new generation of the Upper class in parallel, but this project, originally envisioned as early as 1963, and finalised in 1969 ^[10] would reach production only in 1972. This meant that for the next five years Mercedes-Benz would be constantly releasing new models upon the availability of newer technology into the ageing vehicle to keep it competitive, despite riding on a modified Ponton platform from the early 1950s, leading to a somewhat confusing nomenclature.

The inline six-cylinder engine range was comprehensively revised for 1968. The 2.5 L engine was M108/M129 engine though being a seven point bearing design retained the asymmetrical cylinder spacing of the M180/M127. For further enlargement the cylinder axis were spaced evenly allowing for the motor to be bored out to 2,778 cc (169.5 cu in). It was renamed as the M 130 for both carburetted and fuel-injected versions creating the 280 model series. The former on the 280S model made 140 PS (103 kW; 138 bhp) (DIN) at 5,200 rpm (157 HP SAE at 5,400 rpm), whilst the latter delivered 160 PS (118 kW; 158 bhp) (DIN) at 5,500 rpm (180 HP SAE at 5,750 rpm).

Internal improvements included four piston rings per cylinder were molybdenum-treated for high wear resistance and extended engine lifespan even under sustained maximum load. An air-to-oil cooler replaced the previous oil-water heat exchanger, installed next to radiator as a single unit for more intensive cooling under hard driving conditions. A new camshaft with modified timing improved cylinder filling and torque delivery, particularly in the lower and mid-range engine speeds. Fuel-injected throttle body was now connected to the coolant circuit to prevent icing at low temperatures.

All manual transmission equipped engines now had a diaphragm clutch in place of the coil spring type, which was more resistant to high revolutions, had fewer wear parts, and required lower pedal pressure. The clutch pedal travel was shortened and a spring in the slave cylinder automatically compensated for wear, eliminating the need for adjustment.^[8]

Externally the new models were identical to their predecessors. The interior was redesigned with new fabric patterns, revised colour schemes, and a durable nylon carpet lining the floor at the front, rear, and along the side sills.^[11]

Although the new M130-equipped models were projected as replacements for the 250S and 250SE, production of the former 250S would continue until March 1969, when the surplus cylinder block supply was exhausted. The 280S and 280SE would be produced until September 1972 totalling 184 717 vehicles. Complementing them (until may 1971) would be the W111 280SE coupe and cabriolet, which too got the M130 engine.

New to the lineup was a long wheelbase model, originally also badged as the 280SE, but renamed as the 280 SEL in September of 1969, offering the longer wheelbase of the W109 but on a regular coil spring suspension. Regarding the 300 series, the M189 engine would be retired, and with it the 300SE. However, the pneumatic W109 would continue production and will retain the 300 SEL badging, despite also having the M130 motor. This engine, however, would feature the camshafts from the sporty 280SL Pagoda, generating 170 PS (125 kW; 168 bhp) (DIN) at 5,750 rpm (195 HP SAE at 5,900 rpm). Production of both models, totalling just short of 11 thousand cars, sharing the identical engine and wheelbase, would be prematurely terminated in April 1971 and January 1970 respectively, to make the longer bodies available for the V8 engines.

Following the strong reception of the limited production 6,333 cc (386.5 cu in) 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 the 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 (147 kW; 197 bhp) at 5,800 rpm V8 engine was first fitted to the W 109 in August 1969 as the 300 SEL 3.5 then to the W 108 in July 1970 as the 280 SE/SEL 3.5.

The models were complemented by the W111 280SE 3.5 coupes and cabriolets, launched in parallel with the W109 300SEL 3.5.

With a different crankshaft the 3,499 cc (213.5 cu in) V8 engine was enlarged to 4,520 cc (275.8 cu in) 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 increasing torque for 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 (145 kW; 198 PS) 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 coupés.

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. The 52,622 units sold with V8 engines reflected the market's acceptance of the shift to V8 engines in the luxury car segment.

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 the 280 SEL ended in April 1971, leaving the 280 S and 280 SE as the sole models with six-cylinder inline engines until the end of W 108/W 109 production in 1972, following the introduction of W 116.

Unusual among mainstream European automakers of the time, Mercedes developed and built their own automatic transmission system, first went into production in 1961.^[12]

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.

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.

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.

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.

Wikimedia Commons has media related to Mercedes-Benz W108.

Wikimedia Commons has media related to Mercedes-Benz W109.

• Curbside Classic: 1966 Mercedes 250S (W108) – Cadillac Und Lincoln Kaput – a retrospective of the W108
• Mercedes Benz W108 website
• W108/W109 Tom's Mercedes Benz 108/109 Resource Site
• RollHard - 1972 Mercedes Benz 280SE