Buyers Guide 1991-1999 W140 S-Class Sedans and Coupes and CL-Class Coupes

Richard Simonds


The 1991-1999 W140 S-Class Sedans and Coupes and CL-Class Coupes


The W140 sedans with the S-Class designation were introduced at the Geneva Automobile Show in 1991. They were designed to replace the W126 chassis series that had been the top of the Mercedes-Benz lineup since 1979: It was time to make a statement and the new model did just that. These cars were massive, gaining size in width and height “to accommodate the changing size of humans.” In 1993, a two-door coupe joined the sedan in the lineup, and in 1998, the coupe was renamed as the “CL-Class.”

The sedans and coupes had ample room for their occupants, each cosseted in the most elegant manner of the day.

Yes, the car was massive. The W140s were, in fact, so wide that the side mirrors had to be retracted when the cars were transported on the German rail system because they would not clear the tunnel openings. On some trains, the cars could not even be loaded because of their size. In 1996, perhaps in response to press critics, the W140s underwent a restyling to make then “more graceful” and soften the image of a massive vehicle.

The car was the last created under the direction of manufacturing manager Werner Niefer, whom Dr. Dieter Zetsche once described to be from “the extreme old school, a total traditionalist.” The launch was delayed two years so Niefer could create a car that was more impressive than the BMW 740 sedan, which BMW’s Dr. Wolfgang Reitzle had shown him as a preproduction car. One example of old-school thinking on the 140 was the use of telescoping sight rods – looking like twin antennas – that rose at the back when the car was put into reverse to assist with backing up. In contrast, BMW’s competitive 740 introduced sonar-based parking sensors.

What the W140 succeeded in doing was polarizing automotive journalists, polarizing German buyers, and creating a situation in which Mercedes-Benz sold 100,000 fewer cars than six years earlier. The only market that was not affected by the car’s massive size was Asia. The U.S. market continued selling W140s after initial launch, but only by offering big discounts. It was a big car at the wrong time.

This also was the first Mercedes-Benz model to have a substantial number of systems controlled by electronics – almost every system had some kind of electronic interface. And therein was the problem that would bug users for the first several years: electronic-systems failures. The underlying mechanical systems were generally well designed, but the electronic controls were not well integrated into production. It took nearly a decade for all European manufacturers to realize how critical it was to have strong relationships with suppliers and detailed specifications for components that increasingly relied on electronic communications with each other.

If you’re looking at a running W140 today, the electronics should be well sorted out so you can be more confident about the model than a buyer two decades ago. There were 5-speed manual and 5-speed automatic transmissions available, but the U.S. market only received the 4-speed automatic until 1995, when the 5-speed adaptive automatic became standard. Finally, there were several long-wheelbase models that included Pullmans and Landaulets – seating up to eight occupants – and armored bodies not sold in the United States.

W140 600SEL


The design studios that styled the body made a big effort to reduce the coefficient of drag (wind resistance), which went from Cd 0.37 on the previous model to Cd 0.30. The front grille was canted back and the overall silhouette of the car was sleek and smooth; the trunk was squared to help reduce wind turbulence and allowed considerable luggage space; and the body was larger in every way except wheelbase and length – 2.3 inches taller, 2.6 inches wider – with door openings 3 inches wider. This yielded considerably more interior room: 1.9 inches headroom, 5.5 inches shoulder room, and easier ingress/egress because of the wider door openings.

As the flagship of the Mercedes-Benz fleet, the S-Class emphasized the comfort of passengers in numerous ways. Passengers could benefit from the double-pane side windows that reduced outside noise to a whisper and minimized the transfer of heat or cold into the cabin. Individual climate control systems were available for each passenger, with an activated charcoal filter to purify incoming air. The air conditioning system used the new R134 coolant that was ecologically safer than the R12 Freon from years past. Further, there were self-latching doors and a self-latching trunk lid – no need to slam them shut – and the retracting trunk handle that thwarted accumulation of dirt that might sully one’s hands. A new Bose audio system provided quality sound.

Electronics were used to control the engine, provide brake balancing to improve stopping distances, and to manage the operation of virtually every system in the car: Acceleration Slip Regulation; Active Damping System (available in the coupes); and Anti-Lock Brakes in the 600SE/SEL/SECs. Comfort and smoothness for passengers and improved drivetrain management were the primary reasons for the electronic controls. Once the electronic interfaces were sorted out, the W140 sedans and coupes were exceptional drivers’ cars, handling very well for their size.

The W140 coupes (and the W126 coupes that preceded them) have some of the highest driver loyalty rates of any Mercedes-Benz vehicle ever manufactured. They rarely come on the market and are usually good buys because these owners are not only loyal, but have a passion for the models and the wherewithal to maintain them. Thus, the coupes are particularly collectible. That said, caveat emptor – buyer beware – is still good advice. I personally know several W140 owners who are very satisfied with their cars – other than the costs of ownership – especially for the V-12 sedans and coupes.

W140 500SEL
Reasons to buy a W140

Well-built and durable bodies and mechanical components have fared well

Corrosion resistance continually improved (although road salt in some parts of the country may have allowed the tin worm to do its damage)

Low wind resistance helps maintain a quiet cabin and, given the big engine, improves fuel economy

Comfort for driver and passengers is way above average for cars from this time frame and allows for all-day driving without back aches

These cars make a statement by their very size and presence

Power and smoothness in the W140 are more than adequate, making these supreme touring cars; cross-country trips are very feasible

Safety features – some electronically controlled – were state-of-the-art for the 1990s

Reasons not to buy a W140

As with any classic car, check for rust on the floor pans, quarter panels, door rocker panels, sub-frame mounts, and fender wells

Electronic problems were rampant the first several years, so be sure that all updates and replacements have been made; the cars are long out of warranty and replacing complex systems can be very expensive

There is a known problem with the front suspension; vehicle weight, front-suspension design, and tires can cause vibrations – especially at highway speeds. Some parts should have been replaced under warranty, but be sure to check when driving for severe front-end vibrations that will show up more noticeably when cold

The S600 V-12s are particularly prone to expensive repairs and almost all services will cost more than on an S500 V-8 model. If you are passionate about having a V-12, just be aware that they are high-maintenance vehicles

W140 600SEC Coupe


Rust, rust, rust is always the very first thing to check; corrosion-resistance improvements during the period do not guarantee a rust-free car, especially in places with lots of snow and lots of salt.

Service records from new are highly recommended; this is the only way to be assured that early electronic gremlins were addressed when the car was still under warranty. A very low-mileage car can be more worrisome than one with higher mileage that has been driven and serviced regularly

Suspension components need to be checked for wear and lifetime maintenance; bushings should have been kept lubricated – they otherwise dry out and disintegrate, leading to clunking noises when driving

The LH-Jetronic fuel injection system was new and quite capable, offering more torque over the similar size engine in the W126 system. But like all systems, it suffered from not being driven regularly; check for fuel injection leaks, injector nozzles that are clean and functional, and smooth running from cold start to operating temperatures

Body parts are less likely to be available than engine and drivetrain parts, so look for a car that is complete

Window regulators should operate without any clicking noises; they tend to fail in the down position, leading to worse problems if rain gets in

Motor mounts are fluid filled and can collapse, causing rough vibrations when the engine is idling

Air-conditioning evaporators can leak and require removing the entire dash to repair and replace – entailing eight to 12 hours of labor

Wiring harnesses in 1993-1995 models were designed to be biodegradable and are very expensive to replace

Power steering pumps can leak and, on 600s with the self-leveling suspension, the same pump powers both systems; rebuilding requires six to eight labor hours plus parts.

The plastic oil supply tubes for rocker arms (camshafts) can clog and cut off lubrication, causing a tapping or ticking noise that typically indicates failure is imminent
The door and trunk closing-assist feature is a weak point and can fairly commonly fail

Valve cover gaskets, head gaskets, and fan belt tensioners should be checked regularly to avoid failures

W140 buying tips

Buy the cleanest, best-running, most complete car available, with service records from new

If the residence state has emission control inspections and/or safety inspections, look for a car that has already passed those inspections (according to state laws) within the past 30 days

Personally drive the car that is being considered – or have a person who is knowledgeable about W140s drive the car

An inspection by a professional is recommended before parting with any money because of the complexity of all W140 vehicles; the inspection cost will likely be way less than even one major repair

Final thoughts

If you can find a W140 in good condition, you will discover that it is a magnificent vehicle to own. Because of its size, it definitely makes a statement, but it will also provide a superior touring experience – allowing day-long drives in quiet comfort.  Because of their styling, the coupes are, as usual, the more desirable cars for enthusiasts, but the four-door sedans offer ease of entry and are roomy, comfortable, and elegant. One good friend is a realtor and uses his S500 to take his valued clients to desirable properties.  It may not be totally because of his W140, but he is very successful.

Models & Features by Model Year (MY)
MY1992 300SE, 400SE, 350SDL, 500SEL, 600SEL Sedans debut after March 1991 presentation at the Geneva Auto Show; easier self-latching door mechanism; improved side mirrors & brakes
MY1993 500SEC V-8, 600SEC V-12 Coupes, larger tire sizes; all-new Becker radio models
MY1994 Nomenclature changes with “S” preceding the model number, except in coupes; odometer changed from mechanical to LCD; S420 production started; interior design changes with two colors in S600s; new grille design; steering wheel has wood and leather finish; S600 gets V-12 badging to distinguish it from other S-Class models
MY1995 S320 has revised exterior styling; new long-wheelbase version with four-zone climate control; Parktronic (sonar-based parking assistance) available; radio antenna now roof mounted instead of fender; navigation system available, with navigation CDs mounted in trunk
MY1996 V-8 and V-12 models receive 5-speed adaptive transmission and Electronic Stability Control; Motronic ME 1.0 improves mileage and reduces emissions; S600 Pullman introduced; Acceleration Slip Regulation system provides stability control; interior LED lighting introduced
MY1997 Linguatronic system allows for integrated cell phone; Brake Assist System introduced; enlarged airbags for driver and front passenger; cruise control can be activated only above 30 km/h; rain-sensing windshield wipers; Xenon headlamps
MY1998 Coupes renamed CL-Class, now CL500 and CL600; cruise-control speed is can be selectable at any speed; 400,000th W140 produced November 26, 1997, for a  grand total of 432,732
MY1999  W140 production ends September 1998; W220 S-Class introduced at Paris Auto Show
Value Guide
Model                         Year                 Low                 Medium          High
350SD/S350D             1991-1994       $4,950             $6,300             $8,900
300SE/SEL                  1991-1994       $5,900             $8,000             $10,200
400SE/SEL                  1992-1993       $7,250             $8,300             $12,250
500SE/SEL                  1992-1993       $8,000             $9,350             $11,800
600SE/SEL                  1992-1993       $8,200             $9,400             $12,200
S320                            1994-1999       $5,600             $7,900             $11,500
S420                            1994-1999       $8,300             $9,600             $13,200
S500                            1994-1999       $8,700             $9,900             $13,400
S600                            1994-1999       $8,700             $10,100           $13,600
500SEC/S500C           1993-1997       $8,700             $10,100           $14,400
600SEC/S600C           1993-1997       $8,800             $10,600           $14,900
CL500                         1998-1999       $9,000             $10,500           $15,400
CL600                         1998-1999       $9,100             $11,100           $16,300
Technical Specifications: 1992-1999 W140 Sedans & Coupes
SEDAN           Years               Production      Engine             HP [SAE]        Torque [lb-ft] 
350SD/S350D 1991-’94         14,257             3.5L I6             148                  229     
300SE/SEL      1991-’94         101,123           3.2L I6             228                  229     
400SE/SEL      1992-’93         15,541             4.2L V-8          275                  347     
500SE/SEL      1992-’93         30,833             5.0L V-8          315                  347     
600SE/SEL      1992-’93         17,802             6.0L V-12        389                  420     
S320                1994-’99         20,433             3.2L I6             217                  233                 
S420                1994-’99         12,459             4.2L V-8          275                  347     
S500                1994-’99         22,073             5.0L V-8          315                  345     
S600                1994-’99         7,286               6.0L V-12        389                  420     
Transmission  Rear Axle        0-62 mph        Top Speed      MPG [US]
350SD/S350D 4-A                  2.82                 12.5 sec           115                  20-23
300SE/SEL      4-A                  3.46                 8.9 sec             139                  15-19
400SE/SEL      4-A                  2.82                 7.6 sec             149                  13-17
500SE/SEL      4-A                  2.65                 6.6 sec             155                  13-16
600SE/SEL      4-A                  2.65                 6.3 sec             155                  11-15
S320                4-A                  3.46                 8.0 sec             139                  18-24
S420                4-A/5-A           3.46                 7.1 sec             149                  19-26
S500                5-A                  2.65                 7.1 sec             155                  16-20
S600                5-A                  2.65                 6.5 sec             155                  12-16
COUPE           Years               Production      Engine             HP [SAE]        Torque [lb-ft] 
500SEC/S500  1993-’97         7,104               5.0L V-8          322                  354     
600SEC/S600  1993-’97         7,475               6.0L V-12        389                  420     
CL500             1998-’99          837 [’98]           5.0L V-8          315                  345     
CL600             1998-’99          231 [’98]           6.0L V-12        389                  420     
COUPE           Transmission  Rear Axle        0-62 mph        Top Speed      MPG [US]
500SEC/S500  4-A                  2.65                 6.6 sec             155                  13-16
600SEC/S600  4-A                  2.65                 6.3 sec             155                  11-15
CL500              5-A                  2.65                 6.5 sec             155                  13-17
CL600              5-A                  2.65                 6.2 sec             155                  12-16