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.
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.
Contents
Model description
Development and body design
The car's predecessors, the four door W 111 (1959–65) and W 112 (1961–65), helped Mercedes-Benz develop better sales and achieve economy of scale production by unifying the entire Mercedes-Benz range onto a single automobile platform and body, reducing both manufacture time and cost. However, their signature tailfin design on rear fenders, a popular styling feature of the late 1950s quickly went out of fashion in favour of simplicity and practicality (particularly with regard to manufacture and bodyshop repair). After taking over the design school at Mercedes-Benz in 1957, Paul Bracq began steering the styling away from flamboyance to a stronger emphasis on function. The two-door W111 and W112 models introduced in 1961 were the first to show this approach, which saw the fins drastically rounded off. They were, in turn, followed by the W113 Pagoda and the W100 Größer with perfectly square rear fenders. Work on the replacement for the sedan Fintail body began in parallel, and by 1963 the design was finalised. Retaining the W111/W112 platform and underpinnings, the goal was to maximise passenger space while maintaining the favourably compact exterior dimensions of the previous six-cylinder models, to achieve high levels of safety, ride comfort, and performance. In addition, the top-end W112 sedans had very limited demand, looking too similar to the mass-produced downscale four-cylinder W110 (the diesel versions of which were common as taxicabs) - thus the upcoming new sedans should not share underpinnings with lower-tiered models.
While the external dimensions were increased only marginally relative to the preceding Type 220 S — 25 mm (1.0 in) longer, 15 mm (0.6 in) wider, and 60 mm (2.4 in) lower — the interior space efficiency was significantly improved, primarily by dint of curved side windows and a lowered beltline. As a result, interior width increased by 70 mm (2.8 in) in the rear seating area, and by 90 mm (3.5 in) in the front seating area. The floor in front of the rear seats was lowered by 20 mm (0.8 in), resulting in increased footwell space. The vehicle's centre of gravity was lowered, improving road-holding. The lowered beltline facilitated larger window areas; the windscreen alone was 17 per cent larger than that of the W 111, with total glass area increasing by 12 per cent. The result was a newer-looking, sleeker car with an open and spacious interior. As intended, the flat roof and smooth rear end treatment were stylistically reminiscent of the W111 coupés, W113 roadster and W100 limousine whose sporty and elegant design had garnered worldwide acclaim. The front featured the traditional Mercedes-Benz radiator grille with a wide opening and lowered bonnet and vertical Lichteinheiten lighting units which combined high and low beam headlamps, parking and turn signal lights, and fog lamps into a single, integrated assembly (though U.S. export models used round sealed beam headlamps and separate park/turn lamps in accord with national regulations).
Body construction and paintwork
The body was welded to the chassis floor plate to form a single, torsionally-resistant unit. Vulnerable areas received a seven-layer paint finish consisting of zinc phosphate anti-rust treatment, chromic acid neutralisation, two primer coats, a stone-chip protection coat, undercoat, and topcoat, baked at 130–165 °C (266–329 °F). The underside, inner fenders, door sills, and front valance were given a thick protective coating of polyvinyl chloride (PVC) weighing approximately 14 kg, which remained elastic to prevent stone damage and provide sound insulation. The engine compartment and underside components were sprayed with a wax coating. Chrome-plated exterior trim comprised five layers over steel: matte copper, polished copper, semi-matte nickel, polished nickel, and a double heavy chrome layer.
Interior design and comfort
The seats were developed in collaboration with medical doctors, using firm cushioning to allow small posture changes and prevent the body from bouncing. The backrest followed the S-shaped curve of the spine, and the bucket-shaped design provided lateral support. The driver's seat offered three-way adjustment: fore-aft, vertical height, and infinitely adjustable backrest angle down to horizontal. Multi-layer insulation separated the engine compartment from the cabin: 18 mm at the bulkhead and over 20 mm on sections of the floor. Ventilation air passed through a dust filter; a three-speed blower operated even when stationary. Air was extracted through slots under the rear window, helping to reduce condensation. Heating was independently adjustable for left and right sides. Luggage capacity was 610 litres. Optional extras included an electrically operated sunroof, electric window lifts, power steering, and air conditioning. Twin high-pitched horns were standard; a third horn was fitted to the later 300 SEL 6.3 and 300 SEL 3.5. From the 1968 model year the interior received new fabric patterns, revised colour schemes, and nylon carpet on the floor and sills.
Model differentiation: 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. In turn, the W 111 was a successor to the six-cylinder Ponton models of the mid-1950s; whilst 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: "Größer 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 dividing line between the W 108 and W 109 ran between luxury, performance, and air suspension. The W 109 300 SEL kept the self-levelling air suspension, while the W 108 models from the 300 SEb down retained steel coil springs and a hydropneumatic compensating spring on the rear axle. (A double-acting hydraulic device that used the movements of the swing axle halves to maintain a nearly constant ride height regardless of load). The 300 series were more luxuriously appointed than the 250 series, featuring burled walnut dashboards and fine wood trim. Externally all W 109 models could be distinguished by their door window frames and A-pillars finished with polished metal bright trim. Many optional appointments for the W108 such as power windows, power steering and automatic transmission were standard on the W109, though a fully synchronised manual transmission discount option was available for the latter. Later 3.5 and 6.3 models had a vacuum-controlled central locking system as standard.
Chassis and steering
The front suspension employed a U-profile pressed front axle carrier with double wishbones on each side, separating wheel guidance from springing. Coil springs, gas-filled telescopic shock absorbers, and progressive bump stops were used. A front anti-roll bar was standard; whilst the 300SEL featured an additional rear anti-roll bar. The rear suspension was a single-joint swing axle with a low pivot point; gas-filled shock absorbers prevented oil foaming. The entire suspension was rubber-isolated from the body, and an additional shock absorber on engine mounts damped engine vibrations.
The power steering was a hydraulically assisted recirculating ball design. Below 600 grams of steering wheel force, steering was purely mechanical; above that, a control slide admitted pressurised oil. Road feel was retained, and if assistance failed the car remained fully steerable. The steering system featured a telescopic column, a deformable bushing under the steering wheel, and the steering housing mounted behind the front axle carrier for frontal collision safety.
Air suspension (W 109)
The W 109 300 SEL models were equipped as standard with Daimler-Benz air suspension, developed with Phoenix for the rubber rolling bellows and Bosch for the regulating valves. A compressor drew air through a frost-protection device and delivered it at 16 bar to a reservoir. Three level-control valves (two front, one rear) operated mechanically via rods from the suspension. The driver could select a "high" position via a dashboard switch, raising the body by approximately 5 cm (2.0 in). The system maintained constant ride height regardless of load, allowing a softer spring rate and optimal toe and camber adjustment.
Safety architecture
In the design of the new body by Béla Barényi 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 had a dual-circuit power braking system with disc brakes on all four wheels. The parking brake was a small drum inside the rear disc hubs. A brake force regulating valve on the rear wheels allowed larger rear wheel cylinders for stability during light braking while preventing lock-up under heavy braking. The brake booster supplied approximately three-quarters of pedal pressure. From approximately 1969, the regulating valve was eliminated on the sedans in favour of a constant brake pressure distribution, research having shown it equally reliable for the sedan's weight distribution. On the W109 models the rear brake calipers were connected to the chassis via reaction arms to prevent rear-end lift during braking.
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 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 W 112.
These models were complemented by the W 111 250 SE coupe and cabriolets, which got the stroked M 129 motor, and the W 112 300 SE which retained the M 189 engine.
Whilst the W 108 and W 109 are seen as successors to the W 111 sedans in the segment they held in Mercedes-Benz lineup they did not replace them. The 4 door W 111 230 S, which was effectively the outgoing 220S with a bored out M180 engine will be produced alongside the 250 and 300 series until 1968. It will now share a new market among the newly organised W110 200/200D and 230/230 S series. This marked an important turning point in the separation of the product lines that would no longer be biased to engine displacement, and instead to the car body. Eventually their successors would become the E and S-Classes in summer of 1993.
250 S and 250 SE models
The 250 S 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 considerably greater stiffness and smoother operation, capable of sustaining a maximum engine speed of 6,300 revolutions per minute. The compression ratio was also 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 Bosch 6-point mechanical fuel injection system with a six-plunger pump which calibrated the optimal fuel mixture automatically based on throttle pedal position and movement, engine speed, atmospheric pressure, water temperature, and driving conditions. Such engines received the M 129 designation. 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).
300 SE and 300 SEL models
Both the 300 SEb (standard wheelbase) and 300 SEL (long wheelbase, W 109) were fitted with the 2,996 cc (182.8 cu in) M 189 engine. This engine was an updated version of the M 186, originally developed for the 300 "Adenauer," also with a Bosch 6-point mechanical fuel injection, but featuring a light alloy cylinder block. 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 3.92:1 and automatic transmission, top speed was approximately 185 km/h (115 mph); with the optionally available "faster" rear axle ratio of 3.69:1 in conjunction with a manual transmission, a top speed of approximately 200 km/h (124 mph) was attainable.
Whereas the outgoing W 112 300 SE and its LWB namesake were mechanically identical, this approach was abandoned for the new models. Only the W 109 300 SEL was equipped as standard with air suspension described above, as well as power steering and the four-speed automatic transmission. A manual gearbox was available at a reduced price, and an optional limited-slip differential was offered. The W108 300SEb used standard coil spring suspension of the 250 series.
Production figures
The production figures for the first series from mid 1965 to start of 1968 (spring of 1969 for the 250S) 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.
300 SEL 6.3
The 300 SEL 6.3 was created in 1966 when company engineer Erich Waxenberger transplanted the 6,333 cc (386.5 cu in) M 100 V8 from the 600 (W 100) into the W 109 chassis. Intended to bridge the gap between the 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 presented at the Geneva Motor Show in March 1968 and at the British International Motor Show in October 1968. There are unconfirmed theories that the reason for the car's appearance was also out of necessity due to MB stocking a huge surplus of unused M100 castings, due to the very high price of the Größer.
Daimler-Benz positioned the 300 SEL 6.3 as a long-distance limousine combining optimal comfort with superb performance, acknowledging that the sole criticism of the existing 300 SEL was for greater speed as air-suspended chassis had the effect of making very fast driving feel comparatively sedate. The significance of the model lay in its acceleration: 0–100 km/h (62 mph) in 6.5 seconds and a standing kilometre in 27.1 seconds. The power-to-weight ratio was 6.95 kg/HP (DIN), equivalent to high-performance sports cars. Top speed was approximately 220 km/h (137 mph). Fuel consumption varied between 14 and 24 L/100 km, with a 105 L (27.7 US gal; 23.1 imp gal) tank 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 also carried over from the 600. Due to the size of the engine, the front axle had to be moved forward by 1.5 cm, further increasing the wheelbase. The rear axle was modified with a final drive ratio of 2.85. 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 model was not the first to hide the true displacement of the engine, but the first to specify it separately with the "6.3" lettering on the right side of the boot lid. Externally the look was complemented with three halogen double headlamps in which the dipped and high-beam units were designed as a single assembly, providing longer range and consistent brightness. This headlamp frame design was derived from the US-specification versions to accommodate the sealed beam lenses, but now featured regular halogen bulbs. Initially exclusive to the 6.3, they would become optional on other models. The interior featured a speedometer with an extended range, a standard-fit tachometer, 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.
Second Series (1968–1972)
Market introduction
In 1968, at the Brussels Motor Show in January for Europe and the Chicago Auto Show in February for the United States Mercedes-Benz unveiled the new executive W 114/W 115 "/8" (Stroke Eight); (German: "Strich-Acht") models. Also designed by Paul Bracq, they closely mimicked the W 108 and W 109 models, completing the marque's transition to its corporate style, which began with the two door W 111 models in 1961. Mechanically, however, they rode on chassis and platform of a clean-sheet design, and were slotted below the W 108 and W 109 models to replace the now archaic W 110 and W 111 Fintail sedans, labelled as the medium-class in official press-releases. Mercedes-Benz would embark on development of a new generation of the Upper class in parallel, but this project, originally envisioned in 1966, and finalised in 1969 but would not reach production until 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 still riding on a modified Ponton platform from the early 1950s, leading to a somewhat confusing nomenclature.
2.8 L I6 models
The inline six-cylinder engine range was revised for 1968. The 2.5 L M 108/M 129 engines of 1965 retained the asymmetrical cylinder spacing of the M 180/M 127 predecessors going back into the early 1950s. For further enlargement the cylinder axis had to evenly spaced 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 280 S, made 140 PS (103 kW; 138 bhp) (DIN) at 5,200 rpm (157 HP SAE at 5,400 rpm), whilst the latter on the 280 SE delivered 160 PS (118 kW; 158 bhp) (DIN) at 5,500 rpm (180 HP SAE at 5,750 rpm).
Internal improvements included molybdenum-treated piston rings 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. Complementing it was an optional ZF supplied five-speed manual gearbox from May 1969.
Externally the new models were identical to their predecessors. The interior was redesigned with new fabric patterns, revised colour schemes, a durable nylon carpet lining the floor at the front, rear, and along the side sills.
Although the new M 130-equipped models were projected as replacements for the 250 S and 250 SE, production of the former 250 S would continue until March 1969, when the surplus cylinder block supply was exhausted. The 280 S and 280 SE would be produced until September 1972 totalling 184 717 vehicles. Complementing them until May 1971 would be the W 111 280 SE coupe and cabriolet, which too got the M 130 engine.
3.5 L V8 models
In 1963, following the debut of the M100 motor in the 600 Größer, Mercedes-Benz commenced with the development for the new generation of V8 engines for its executive range. Unlike the M100, which stressed the chassis to the limit and its extreme cost left it for a very specific clientele, the new 3.5 L M 116 motor was to become the primary engine for the next generation of cars, for both the US market and in Europe, as the motor was developed in anticipation of revision the German taxation law on displacement, which was published in May 1969 reducing the penalties on engines exceeding 2.7 litres.
The engine was a 90° V8 with grey cast iron block, light alloy heads, bore × stroke of 92 mm (3.62 in) × 65.8 mm (2.59 in) (stroke-to-bore ratio 0.715:1), and maximum engine speed of 6,500 rpm. The short-stroke design and placement of the intake manifolds between the cylinder banks made the V8 lower than the six-cylinder in-line engine. Weight was approximately 225 kg (496 lb), only 13–18 kg (29–40 lb) more than the M 130.
The M 116 featured forged and nitrided steel crankshaft with five 64 mm main bearings, molybdenum-coated pistons, cross-flow wedge combustion chambers with sodium-cooled exhaust valves, rotocap valve rotation joints and one overhead camshaft per bank driven by duplex chain with hydraulic tensioner. A major milestone was electronically controlled Bosch D-Jetronic fuel injection eliminating the mechanical injection pump and the large intake pipes. The electromagnetic injectors fired in four groups of two per one crankshaft revolution with a control unit that received inputs for intake manifold vacuum, engine speed, air temperature, coolant temperature, and throttle position; idle mixture adjustable via potentiometer. Transistorised ignition also made its introduction with the M116, such that contact breaker points carry only low control current, preventing their burning. Cooling included a visco-drive fan and thermostatically controlled electric auxiliary fan.
The engine was first fitted to the W 109 in August 1969 as the 300 SEL 3.5, presented at the Frankfurt Auto Show alongside the W 111 280 SE 3.5 Coupé and Convertible (whose fascia would be redesigned with a wider and lower grille). Output was 200 PS (147 kW; 197 bhp) (DIN) at 5,800 rpm (230 HP SAE at 6,050 rpm) with 29.25 kp⋅m (287 N⋅m; 212 lb⋅ft) of torque at 4,000 rpm. Acceleration from 0–100 km/h took 9.0 seconds. Standard equipment included the Mercedes-Benz four-speed automatic transmission (with three planetary gear sets giving in-gear maxima of 40, 88, and 148 km/h), air suspension, power steering, central locking, electric windows, and a three-tone horn. Top speed with the automatic was 205 km/h (127 mph); an optional manual gearbox raised it to 210 km/h (130 mph).
4.5 L V8 models
The M116 powered 300 SEL 3.5 was introduced to the United States for the 1970 Model year at the New York International Auto Show. The 1970 amendment of the Clean Air Act, stipulated reduction of Nitrogen Oxide emissions, which would result in lowering of compression ratios and reduction of fuel octane levels. To compensate for this, and to stay competitive in its top export market, Mercedes-Benz stroked the M116 by 19.2 mm, raising the displacement to 4,520 cc (275.8 cu in). The 4.5 L V8 engine was designated as M 117 and made 195 hp (145 kW; 198 PS) at 4500 RPM, falling just short of the domestic 3.5 L V8 engine. However, it did generate 36.5 kp⋅m (358 N⋅m; 264 lb⋅ft) of torque at 3,000 RPM, 25 % more than the domestic 3.5, at which it was considered sufficient that the MB to pull the 6.3 out of the US export market for the 1972 and 1973 MY. The M117 was coupled with the new W4A 040 three speed automatic which introduced a torque converter.
The models would be respectively called 280 SE 4.5, 280 SEL 4.5 and 300 SEL 4.5. Sold exclusively to the United States, they would close the W108/W109 and thus the whole Ponton era in November 1972, in a small production overlap with the W116. A total of 24 253 cars would be delivered. Incidentally the M117 would remain exclusive to the United States until mid 1973 for the next generation of 450 series for the 116 and 107 S-class chassis.
Transmission
Unusual among mainstream European automakers of the time, Mercedes developed and built their own automatic transmission system, first went into production in 1961.
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.