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Mercedes-Benz 126 SEC

Mercedes-Benz 126 SEC Published: 10th Sep 2019 - 0 Comments - Be the first, contribute now!

Fast Facts

  • Best model: 560
  • Worst model: 380
  • Budget buy: 380/420
  • OK for unleaded?: Yes
  • Will it fit in the garage? (mm): L4940 x W1830
  • Spares situation: Generally quite good
  • DIY ease?: Not too bad
  • Club support: Typically Mercedes
  • Appreciating asset?: Just started to pick up big time
  • Good buy or good-bye?: Cultured coupé for sure, but take care buying one
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S-Class-based coupé that’s rapidly becoming collectible. Oozes quality, class and value if you buy well – but it’s a fearfully expensive modern classic if you don’t…

Unlike their desirable drop tops, Mercedes coupés can hit and miss as classics. The W107 range is a case example where the convertible grabs all the attention whereas the stretched SLC still lives in its shadows. Until quite recently, the larger S-Class-based SEC was even more unfairly ignored, gaining a glorified banger status and falling into the hands of blingers and those after a bit of posh for pennies.

However, the tide is fast turning for the W126 pillarless two-door coupés and the best of the rest are fast gaining collector’s status. Look at one as a ‘Mercedes XJ-S’ but sturdier, more imposing looking and arguably classier.


1979 Exquisite all new W126 S Class saloon is launched and is soon lauded as the best saloon in the World with advanced safety features such as airbags, seat belt tensioners and traction control.

1981 SEC spin off introduced based upon the S-Class platform but shortened by four inches, albeit still over 16ft long and the body is steel with aluminium boot and bonnet – all beautifully in proportion, unlike SLC. Two engines are initially offered, being twin cam V8s which denotes their model designation. The 380 has a 3839cc engine developing just over 200bhp while the 500 provides 231bhp from 4973cc but importantly over 70lbft of extra torque, both mated to a four-speed automatic.

1985 Facelift sees uprated engines sporting electronic ignition with the 380 becoming the 218bhp 420 while the mighty 5547cc signifies the flagship 268bhp 560, identified by flared wheel arches. The 500 remains however, now up gunned to 242bhp.

1987 Engines are given slight power boost by way of increased compression ratios upping the 420 SEC to 228bhp, the 500 SEC to 261bhp and the 560 a whopping 296bhp.

1991 Production ends after almost 75,000 were made. Breaking the figures down, the 500 was the best seller (30,184) just ahead of the 560 (28,929). In contrast, just over 11,000 380s were built, and only 3680 420s.

Driving and what the press thought

At the time of the S-Class launch, Mercedes and Jaguar were vying to be considered as world beaters and so the standards were becoming extremely high. The SEC is a special occasion classic which can’t fail to impress.

Perhaps the Jag is more serene because, in common with that other German, Porsche’s 928, the SEC exhibits a tad too much tyre and road noise and the ride isn’t so supple as the XJ-S or XK8 (facelift cars feature a revised rear suspension that improves the ride and handling-ed) but, the airier, more spacious cabin, makes the Mercedes by far the more accommodating GT with an outstanding 33mph/1000rpm stride causing one road test to remark, “it’s difficult to see how this engine could be worn out by use”.

The sweet running 380 was never popular but, if you Find a good one, its 200bhp appears entirely adequate if you don’t wish to tear around. But it has to be said the 500/560s are hugely entertaining thanks to their muscle-bound performance which doesn’t require your own fuel station to run as 20mpg+ is quite attainable say owners. However, overall the 420 occupies the logical middle ground.

Upon its launch in late 1981, monthly CAR gushed with praise. “These spectacular Mercedes two-door are more than a new coupé of the world-beating S-Class; they bring a round of technological breakthroughs.… what’s more, they’re sky high on desirability”.

Twelve months later, the same tome pitched the 560 SEC against the Aston V8 (feeling that the XJ-S was more a 300 CE rival-ed). quickly noting that the German was very much “made for the 80s and 90s where eficiency is all”. The test further remarked that the ride quality “is the best we know we this side a Citroën” but thought a “ponderous” steering sullied the SEC but predicted that ABS would one day become a life saver…

The Aston, not unexpectedly, had the 560 SEC well beat on out-and-out performance “Yet it’s clear”, said the twin test “that the Merc is today’s car” citing everything from a lower price tag and longer servicing intervals to better parking protection. Odd then, that five years later, it labelled the SEC in its famous ‘The Good ,The Bad and The Ugly’ buying guide as “Totally dependable but unexciting” and two years later criticised the car’s road noise and silly pricing (£63,000 for the 560 SEC, – about what a concours car might make today-ed) and called it more or less an “extravagant saloon”.

Classic caring

It may be fast becoming a 40 something, but the SEC – with traction control and self-levelling rear suspensions – is still a complex piece of kit that you have to buy and maintain with care, and you’d be unwise to purchase any runner without some semblance of service history. Preventative maintenance is the key, preventing minor problems not escalating into expensive major ones. Here’s one example: the electrical contacts in the door jamb can become dirty, which can sffect the interior lights, seat belt extenders and an assortment of warning lights and buzzers.

Projects can seem absurdly cheap but restoration costs can be colossal as well – in all honesty, their values mean that the SEC is not a classic worth restoring yet. There’s good and bad news for owners though: On the one hand, spare parts are still available from main dealers (although nowhere near as prevalent as before say M-B specialists), the flip side is their cost. Help is also at hand from an army of independents and a very active owners’ club ( Specialist servicing costs hover around £200-£600 depending on mileage.


Although an AMG derivative was offered, the SEC is not really a car to mess with, although many have done, to its detriment, usually fitting lowered sports suspension and over wide wheels, undoing all the company’s intensive development. This Merc also seems to attract customising and bling, sullying the car’s uber classy image. Any modifications should be done sympathetically after consulting specialists although early models sans electronic ignition are well advised to be brought into the 21st Century and we’d think about replacing the radiator purely as preventative maintenance.

That body beautiful

Check that sleek coupé with great care because all that glitters may not be sound metal as Mercedes’ hitherto impregnable build quality was starting to slip. Biggest common concerns include the front bulkheads (similar to the R107 albeit in different areas), the rear window parcel shelf (caused by leaky seals – an expensive window out repair) and the battery tray area. Dealer Charles Ironside warns the rear screen is the major danger area.

You really need to get underneath to examine carefully the front subframe and the anti roll bar mounts along with the suspension turrets for the red ruin. The sills are also rot prone, chiefly by the acting points.

Be wary of blinged bodies sporting custom kits such as chrome wheel arches. Apart from being tacky and difficult to remove without damage, such dubious decorations can craftily mask hidden rust spots and most Mercs rot at the front wings and wheel arches. All cars are susceptible to corrosion but pre 1986 cars are claimed to be the worst.

Inside information

While leather trim was available, a great many SECs were decked in voluptuous velour as it was oh so fashionable during the 80s. This trim can age and sag, along with the headlining. If the interior gets damp (usually due to faulty door and window seals or a leaking sunroof) it can cause the German wood to lift. Ah the sunroof! Sounds a desirable fitment yet can be the bane of the SEC as it can be extremely difficult and expensive to repair – check that the roof works properly and scrutinise the carpet and floor for dampness, indicating leaking seals. There’s lots of electrical toys to play with – check they still work and that goes for all the dashboard lights which may have been ‘doctored’ to hide a fault.

Values and specialist view

Values are all over the shop, ranging from 10k to over five times this. With rare exceptions, SECs under ten grand are a rusting liability and you need to spend double this for peace of mind although don’t expect perfection! Spending the thick end of 30K entitles you to look at stock from classic car dealers and marque specialists while anything above is 500/560 territory and the best SECs are easily making this money.

Edward Hall says SECs are currently pretty hot stuff but says condition is king and it’s better to have a superb 420 than a so-so 560 SEC and cheap SECs “are for breakers” in his view. Also, unlike SLs which could be purchased as playthings, buyers of SECs (such as company big wigs) tended to use them to the full.

Specialist, Charles Ironside agrees, adding that their popularity has taken a turn since the spring. He tries to avoid customised cars and only goes for the best ones, which are becoming harder to track down. In his view, the 500/560 are the best buys, the 420 some way behind and is reluctant to touch a 380, not simply because of its flaccid engine, but also the bodies weren’t galvanised.

Great V8s

These all alloy M16 and M117 V8s are almost unbreakable if serviced properly which includes regular replacement of anti-freeze to keep the anti-corrosion properties up to speed. If there is a weak area then its their timing chains and camshafts: If you hear a light knock upon start up it’s a sure sign that the chains are becoming worn but a continual rattling mostly indicates possibly the camshafts as well are failing – and both cost well over £1000 each to put right. The hydraulic engine mounts are known to fail costing £600 to supply and fit. Other faults are electronic with the ignition becoming temperamental. Don’t instantly assume that poor running is just worn spark plugs and be wary of steam cleaned engines, warns one SEC expert, as a stray jet of water can mean a grand to put right! Finally, do those glorious V8 sound right? Don’t dismiss a blown exhaust lightly as a proper Mercedes set up can cost well over £2000 and for that money we’d look to a stainless exhaust manufacturer!

What To Look For

Running gear regs

All high quality as you’d expect but pricey when it goes belly up. The automatic transmission is long-lived but a good health check is to see how long reverse takes to take up drive. The forward ratios should be smooth with no slipping and if anything’s amiss you’re looking at a £1500 rebuild.

The SEC is a big heavy coupé and this takes its toll on the suspension in the shape of tired dampers and springs, although notable listing can also be due to the self levelling rear end playing up. The SEC’s Achilles Heel appears to be the front steering ball joints which, when worn, clonk. Nothing serious, but special tools are required to replace. Worn steering boxes and their idlers are also common. The only issue with the SEC’s powerful brakes appears to be the old school ABS and defective sensors. Other than that, it’s the usual worn discs and rusty hydraulic pipes to contend with.

Finally the wheels and tyres. Facelift cars ran on 15inch rims and 205/65 tyres, the exception being the 560 model (215 section). It’s a good chance that custom aftermarket rims have been fitted but their quality varies and one day originality will count – ask if the originals still around. A good sign of careful SEC ownership is the warm feeling of seeing uniform quality tyres of the same make, or at least in axle pairs.

Three Of A Kind

Jaguar XJ-S
Jaguar XJ-S
This XJ12-based GT is a main rival and those odd looks are now starting to appear classical. Most favoured are post ’91 models with their revised looks. V12s are magnificent but the AJ6-engined models are easier to own, more than quick enough and surprisingly frugal. A good well sorted XJ-S is a joy to drive and own and still amazing value – but not for much longer we’d wager…
BMW 8 series
BMW 8 series
BMW’s super suave 8 Series is only just receiving the plaudits it genuinely deserves. Initially it was V12-powered before an equally good 286bhp V8 (840i) joined the range. Like the SEC, this fellow German is most at home when touring but the 380bhp, 5.6-litre CSi is as good as many established supercars. Complexity means maintenance and repairs can easily outweigh the car’s value and many cars are neglected.
Bentley GT
Bentley GT
Frightening depreciation has resulted in the awesome Bentley GT becoming temptingly affordable at around £20,000. Given their heart-stopping service and repair costs, buying a cheap one is a gamble but what a car if you strike it lucky! It may be little more than a re-bodied Volkswagen Phaeton saloon but you won’t find a more competent and classy V12 AWD supercar anywhere else at any price.
Classic Motoring

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