The Best of the Best: The U.S. Market W126 S-Class 1981-1991

Article Pierre Hedary & Gary Anderson

Contributions Daniel Stahl & Richard Simonds Images Daimler Archives

Few luxury sedans survive long enough to become classics; fewer still are actually affordable by the average enthusiast. The W126-chassis Mercedes-Benz, produced for a stunning 12 years from 1979 to 1991 and sold in the United States from 1981, is a strong contrast in both respects. The W126 was, according to many experts and marque aficionados, the best S-Class Mercedes-Benz ever made. 

Examples that received the care and respect they deserved when new are still being driven today. In fact, enough of them have survived in excellent condition that they are not only affordable as entry-level classics, but are even good values for the person who wants a daily driver that is luxurious, stylish and easy to work on for the price of the cheapest new econobox.

Background

In the years following the 1973 gasoline crisis and the furor arising from Ralph Nader’s book Unsafe at Any Speed, automotive manufacturers were challenged to meet increasingly stringent safety requirements, as well as higher standards of fuel efficiency. Mercedes-Benz had been testing a gasoline-powered aluminum-block V-8 and a high output [for the time] turbocharged diesel engine, and was already selling its 2.8-liter twin-cam six in the W116 sedan, introduced in 1973.  The W116 car was a well-made car, but the climate control, U.S. bumpers, emissions systems, and other components needed further development to meet world requirements; a completely new design was required to fully address these outstanding issues.

Mercedes-Benz complied: In 1979, the first new W126 Sonder Klasse (special class) models – the 380SE, 500SE and 280S – were delivered to showrooms in Europe. Two years later, the company introduced the 380SEL, the long-wheelbase version of the 380SE, and the 300SD diesel-engine version of the W126, to customers in the United States.

The 300SD was an instant hit. Sales took off and the big sedan won Motor Trend’s Car of the Year Award, a first for such a large vehicle. Extremely well-made, nicely-optioned 300SDs – often pictured in the light ivory color that graced Mercedes-Benz sales brochures – are still a common sight on today’s roads.

The long-wheelbase, gasoline-powered 380SEL did not fare so well. The V-8 produced an anemic 155 horsepower. As smooth as the engine was, timing chain problems were its Achilles’ heel, and Mercedes-Benz technicians were soon plagued with complicated and expensive chain replacements. The stylish but still mechanically challenged 380SEC coupe joined the lineup for model year 1982.

In terms of the gasoline-powered cars, many owners went further afield. The thriving gray market captivated the imagination of many Mercedes-Benz customers, and private dealers began bringing high-performance European W126 cars into the country by the dozens, federalizing and reselling them to eager clients. When companies like AMG, Brabus, Schulz and others joined in the customization and performance party, things got even better.

In 1985, ABS became standard on the W126, heralding a new era of performance and safety. In that same year, the U.S. lineup included the 500SEL, 380SE and 300SD. These models were replaced by the more powerful 420SEL and 560SEL/SEC in 1986. Handsome and refined, one of these new V-8 flagships became the luxury automobile to own if you wanted a big sedan.

On the other hand, the 300SDL with the OM603 turbodiesel that replaced the 300SD in 1986 suffered at the start with cylinder head issues. Thankfully Mercedes-Benz updated the heads with improved versions, but the model was still withdrawn two years later.

Meanwhile, standard airbags and automatic seatbelt tensioners were added to protect drivers of these increasingly fast sedans. In 1988, the 300SE and 300SEL joined the line-up; in 1989, interiors, cooling systems and exterior panels were updated. In 1990, the 350SD/SDL joined the lineup, and the last W126 cars were sold in the United States during the closing months of 1991. 

The number of these cars still on the road attests to their workmanship and reliability. The quality of the W126 range is so high that many perfect examples still exist. Few can dispute the charm, elegance and practicality these cars still convey.

Reasons to Buy

Safety, reliability, and comfort made them excellent for daily driving or long-trip touring

Heating and a/c systems were significantly improved and made a W126 comfortable and usable all year around

Engines (both gasoline and diesel) and drive trains were increasingly robust and long-lived with proper maintenance

Interiors (especially M-B Tex) are durable and easy to clean

Values are exceptional at this point in their life cycle (27-36 years old) but are expected to begin appreciating for well-cared-for, preservation-class vehicles

Diesels get mileage comparable with new Mercedes-Benz diesels (high 20s to low 30s on the road)

The W126 is still contemporary looking and offers comfort for passengers, plenty of luggage space and excellent visibility

Reasons Not to Buy

Many examples for sale suffer from lack of maintenance, which may not be readily apparent in a casual inspection

Genuine OEM Mercedes-Benz parts are relatively expensive and may not always have been used in servicing

Aluminum-block engines were vulnerable to overheating, especially if coolant systems were not carefully maintained

Gasoline-engine models are not as fuel efficient as diesels, especially compared with modern cars

In spite of excellent rust protection, the elaborate design of the body makes it vulnerable to rust, which is easily camouflaged and expensive to repair

Checkpoints

Early 380SE/SELs should be checked for timing-chain updates, with chain guides, chains and tensioners replaced

Excessive oil consumption, especially on gasoline engines, may mean worn valve guides or head gaskets; this is an indication of an engine in need of rebuilding

350SD/SDL engines are particularly prone to damage from overheating, and to rod failure; check maintenance records for proof that the engine has been recently replaced or budget for engine replacement

Bio-diesel or vegetable oil conversions should be avoided because the lubricity and cetane rating of these fuels can lead to catastrophic engine failure

Plastic radiators are prone to leakage and cracking, which may also lead to overheating and engine wear

Front-suspension ball joints and bushings are prone to wear or failure and require specialized tools to replace

A/C compressors should be checked for effective operation, ensuring cold air is produced from center dashboard vents; if necessary, replace with a new Behr unit

HVAC defroster vents should close completely when a/c is operated, otherwise a/c actuators may need replacement. A/C repair is complicated because of dashboard design

Seats that sag indicate broken springs and worn-out horsehair pads; torn or cracked leather or MB-Tex may need replacement

Dashboards with cracked vinyl, worn leather and discolored or damaged wood trim are likely to be expensive to restore

Rear-window glass is prone to delamination, leading to rust in rear shroud sheet-metal panel

Back-door vent windows operate by sliding-jaw gear. A replacement part is made; replacement is complex and costly

Airbags should be replaced every 10 years on all cars; check if this was done by an authorized Mercedes-Benz Center

Buying tips

If you are a first-time W126 buyer, look for a 300SD. These cars are known for clocking over half a million miles with no real problems. They are easy to start in all conditions, are quiet and quite powerful, and good examples are easily found. While the model was known for cylinder head issues, most still-running examples have been sorted, and the result is impressive – a comfortable and quick diesel sedan that gets 28 mpg or better, with little noise and no turbo lag.

The successor 350SD was known for connecting rods unable to handle the engine’s torque; many units had to be rebuilt under warranty. Many machinists also agree that these engines would leak oil through their valve guides, and on colds starts, the fluid pressure on top of the piston could damage the connecting rods. Poor fuel quality, lackluster maintenance by some owners, and stop-and-go traffic all conspired to damage these engines, marring their reputation. However, these can be fantastic cars when their engines are “right.” 

The best gasoline-engine model is the 1988 300SE/SEL with its bulletproof easy-to-service, I-6 M103 engine. It’s not as fast as the V-8s, but has better balanced performance and is easy to service. A detailed prepurchase inspection, with partial disassembly of the engine to check for timing-chain servicing, head-gasket condition and possible valve wear is money well spent unless you’ve budgeted for a rebuilt replacement engine.  Alternatively, a well-sorted 420SEL or 560SEL is a hoot to drive.

In Europe, a 500SEL was available with four-wheel hydraulic suspension. These gray-market cars are not for the faint of wallet, but handling is beyond anything else Mercedes built at the time. The option was offered on some 560SELs, but this model is difficult to find.

When reconditioning interiors, use Mercedes-Benz horsehair pads and ensure that the grain of the leather is correct. Many suppliers are selling incorrect rough-grain leather, which is also less attractive and uncomfortable. Most interior trim is still available from Mercedes-Benz or the leading interior-trim suppliers, though it will be costly.

While gray-market cars were once frowned upon, these models have now come into their own. While their velour interiors are hard to get repaired, the high-horsepower Euro engines with manual gearboxes are exciting to own.  AMG did some wonderful things with bodies and power plants, making the W126 its flagship, and attaching twin-cam heads to the V-8 engines. In states such as California, make sure your car can pass the emissions test before you buy it.

The best W126 cars are still under $15,000, though AMG versions can fetch as much as $50,000. As they become more collectable, their value will only rise. These cars pay off in the long term, as many satisfied owners can attest. Even with the cost of service, these cars deliver more than you have to put into them, and with reasonable care are likely to continue to do so for decades to come.

Chronology

1979       First W126s (280S, 280SE, 380SE, 500SE) delivered in Europe

1980       280SEL, 380SEL and 500SEL joined the range in Europe

1981       300SD and 380SEL put on sale in the U.S.

1982       380SEC and 500SEC introduced (the 500SEC in Europe only)

1984       In the United States, 380SE and 500SEL replace 380SEL; 500SEC replaces 380SEC

1985       ABS now standard

1986       300SDL replaces 300SD; 560SEL and 420SEL replace previous gasoline models;

               560SEC introduced in the U.S.; airbags and KE-Jetronic fuel injections now standard

1988       300SE and 300SEL replace the 300SDL in the U.S.

1990       350SD and 350SDL introduced in the U.S.

1991       Last W126 series are sold, to be replaced by the W140 series

Specifications: Mercedes-Benz W126 U.S. Models

Sedans: Model Years  Chassis        Engine                     Power  Torque

300SD   1981-1985     126.120      617.951      1981-83: 120  170

                                                                           1984-85: 123              184

                                                                           1985: CA:118   177  

     Global Production 76,726

380SEL  1981-1983        126.033   1981:      116.961

                                                        1982-83: 116.963       155  196     

     Global Production 27,014

380SE   1984-1985     126.032   116.963         155  196     

     Global Production 58,239

500SEL  1984-1985     126.037    117.963       184      247     

     Global Production:  72,693

300SDL  1986-1987    126.125     603.961    1986 Fed: 148   201

                                                                        1986 CA: 143   195

                                                                        1987:       143   195     

     Global Production: 13,830        

420SEL              1986-1991     126.035           116.965           201      228     

     Global Production: 74,017

560SEL              1986-1991     126.039           117.968           238      287     

     Global Production: 75,071

300SE    1988-1991     126.024           103.981           177      188     

     Global Production: 105,422

300SEL   1988-1991     126.025           103.981           177      188     

     Global Production: 40,956

350SDL  1990-1991    126.135           603.970           134      229     

     Global Production: 2,925

350SD   1991               126.134          603.970           134      229     

     Global Production: 2,066

Coupes:  Model Years  Chassis No.   Engine No.     Power   Torque    

380SEC   1982-1983    126.043           116.963           155      196     

     Global Production: 11,267

500SEC   1984-1985    126.044           117.963           184      247     

     Global Production: 30,184

560SEC   1986-1991    126.045           117.968           238      287     

     Global Production: 28,929

W126 S-Class Sedan

W126 S-Class Coupe

Front and rear three-quarter views of the handsome 560SEC coupe.

A cutaway drawing of a W126 S-Class sedan.

Head of Mercedes-Benz styling, Bruno Sacco, with scale a model of a W126 coupe.

The W126 interior is both classic and contemporary, with advanced safety and comfort features, including an airbag and an early on-board trip computer (right-hand gauge in instrument binnacle).

The U.S.-market 300SDL turbodiesel and 300SE.