Big saloons didn’t come much classier than the W108/9 – at least until the S-Class came along – but they remain easy to live with
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Words: Jon Burgess Images: Beverly Hills Car Club
Succeeding the much loved W111 and W112 ‘Fintails’ was a daunting task – but Mercedes-Benz rose to the occasion. With the W108 and W109, Mercedes-Benz reorganised its post-war model range before the rationalisation of the Eighties – and the need for a small executive car – took over. It was increasingly heading towards mass-production of high-value cars, the coach built, hand-made exclusivity of the likes of the Adenauer series receding into the history books by 1962.
The ‘Fintail’ cars were the first to bring assembly line rationalisation to the upper end of the Mercedes-Benz range; while the W100 Grosser would continue the old methods in small numbers, the entry-level Ponton and 190 series were churned out in their thousands.
Rearranged for the mid-1960s, the W114/W115 sat at the bottom (succeeded by the W123) the W108/W109, split by wheelbase, trim and suspension in the middle, with the W100 ‘Grosser’ at the top (its mantle later inherited by increasingly bespoke iterations of W126 and W140 S-Class).
The Paul Bracq-styled W114/W115 brought an end to the flashy tail fin (Heckflosse) aesthetic of earlier Benzes: his W113 SL ‘Pagoda’ did away with them, too, and, eventually, the Grosser followed suit.
Mercedes-Benz realised that long-wheelbase variants of its upper tier cars were still popular: hoping to court well-heeled owners whose means meant the Grosser was out of reach, the W109 inherited the ‘L’/Lang designation, if specified, with an extra four inches of space in the rear seating area, and 10cm longer aft doors.
The 300SEL moniker had served the W112 well; a similar strategy was applied to the W109, its brightwork polished stainless rather than the anodised aluminium of the W108. The former car stuck with coils and dampers, whereas the latter car used self-levelling air suspension, as befitted its status, which also included wooden dashboards, automatic gearboxes, electric windows – and the larger, 3.0-litre six pot.
That’s the W108/W109 separated; how (and when) were the models launched? The place was the Frankfurt IAA, and the year was 1965: the W108 range consisted of the 250S and 250SE, while the sole W109 was badged 300SE or 300SEL.
By 1967 the second series of cars were ready: the 250 S and 250SE became the 280S and 280SE, with a long-wheelbase 280SEL added to the W109 range. There was still a 300SEL, but that too had a 2.8-litre engine with 168bhp, instead of the 140 or 158bhp of the 280S and 280SE.
A limited-run, high performance version of the 300SEL, the 300SEL 6.3, arrived a year later as the range-topping W109; as the US began to demand more power from lesser models, the 300SEL 3.5 V8 arrived in 1969, with Bosch D-Jetronic fuel injection. The engine migrated to the W108 a year later, badged as the 280SE 3.5.
Emissions legislations dragged the performance of the M116 3.5-litre V8 down, so a larger 4.5-litre variant, the M117, was introduced for 1971 for US buyers, in 280SE/280SEL/300SEL 4.5 guise. The upcoming W116 S-Class, which replaced the W108/W109 in 1972 and R108/R109 SL would inherit these V8s as a basis for improvement.
Engine, transmission and mechanicals
None of the chain-driven engines fitted to the W108/W109 give trouble if the oil change intervals – between 2500 and 5000 miles – are adhered to. The Zenith carburettors fitted to earlier 250 S and 280 S models are served by rebuild kits and (very) expensive replacements should they be needed.
Inspect the exhaust manifolds on the 3.5-litre V8s regularly, as they can crack through age, heat cycling, or lack of use. Radiators can silt up, but regular 24 month coolant changes can obviate this.
D-Jetronic fuel injection can be taken care of by classic Mercedes specialists; Mercedes-Benz itself and Bosch Mobile Tradition will sell you service kits as and when needed. Checking the high pressure fuel lines regularly will pay dividends. Replace any rubber fuel line with ethanol compatible R9: vacuum lines are also worth checking during service bay time.
Manual gearboxes, by column change, rarely falter. Mercedes-Benz stubbornly persisted with its fluid coupling auto, which held the revs high and shunted ratios; that sort of behaviour in normal use is to be expected. Periodically inspect the kick down cable and make sure the ATF levels are clean and where they need to be: rule of thumb is every three years or 40,000 miles.
W108/W109s go through kingpins if they’re not lubricated: check them at every oil change interval. You’re looking at three per side: one on the kingpin itself, and one each on the upper eccentric kingpin joint and the lower kingpin joint.
While you’re there, check both lubrication points per upper and lower control arm, too: it’s all available but preventative maintenance trumps replacement. Springs and dampers on W108s are relatively simple to replace, save for the hydropneumatic rear leveller, make sure it pumps back up under load every time you take the car out. For the air suspension of W109s, entrust this to a specialist familiar with the model: the Beverly Hills Car Club, or local Mercedes-Benz group can advise.
Steering boxes are another point of contention: while they last a long time, make sure everything in the system is free from play – and that what little oil it does use is topped up to the level.
Bodywork and interior
90 per cent of the brightwork is available still from Mercedes-Benz – and what it can’t supply, breakers, specialists and the aftermarket can help with. It’s all expensive, mind you, so keep them clean and polished.
Remember that W108 and W109 used differing materials for their brightwork – and that SELs had longer doors in case any replacement panels are needed.
Whether your W108/W109 is kept indoors or out in the open, periodic checks in key places of the bodywork will keep it looking fresh. Rust can creep in on the front wings around the bottom edges of the headlights and on the bulkhead, the battery tray and rear wheelarches.
The MB Tex fitted to most W108s is hard wearing but available if it eventually succumbs; the leather and wood of the W109s is rather harder to source if it starts getting tatty. Budget significantly if the heater fan sounds unwell: it’s a big job to sort if a replacement part is needed.
Finding a good example
No longer hidden in classifieds or used daily (though well-maintained examples are still more than up to the task), the W108/W109 is a car found at dealerships, at auctions or traded between owners of your local Mercedes-Benz club.
All can keep up with and cope with modern traffic without uprated brakes or cooling, but some are more equal than others at that particular task. The performance of the 6.3 is impressive even today, but its running costs and complex air suspension mean that it will extract the biggest toll on your wallet.
At the other end of the spectrum, the carburetted 2.5 and 2.8 cars remain the most affordable, with jobs tackled at home by a competent mechanic. If the budget permits, enthusiasts rate the 3.5-litre V8 cars with their balance of performance, handling and luxury. US spec automatics shift more smoothly than their European counterparts, as they have traditional three-speed torque convertor automatics.
Beverly Hills Car Club has a number of W108/9 models in stock at time of writing, including the 300 SEL 6.3 you see in these pictures.
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