The Star® Journal

Article: Richard Simonds
Data Tables: Daniel Stahl
Images: Daimler Archives

Writing in Road & Track magazine, the great automotive journalist Tom McCahill identified the mighty Mercedes-Benz 300SEL 6.3 as "Merely the greatest sedan in the world." The 300SEL 6.3 was also considered "The Gentleman's Hot Rod" at the time. Even the basic W108 250S sedan was singled out: "The near-perfect mating of suspension, brakes, power plant and functional design makes it one of the most desirable 'sports sedans' in the world."

Following up on the W110-W111 series Finback sedans, the design of the W108 included unibody construction with "safety zones" designed to crumple on impact, a padded dash, seat belts, headrests, recessed door handles, a collapsible steering column mounted behind the front axle rather than in front of it, and a spring-mounted rearview mirror designed to break away if struck. In 2010, the authoritative website MercedesHeritage.com referred to the model range as: "The 108 chassis: the perfect entry level classic Mercedes."

The short-wheelbase models had a 108.3-inch wheelbase; the SEL models stretched out to a 112.2-inch wheelbase. The W108 series had coil springs; the W109 had air suspension. Offering several different engines over the production run, the sedans were available in 250, 280 and 300 versions with in-line 6-cylinder engines and 3.5L, 4.5L and 6.3L V-8 engines. Today, the 108 and 109 series sedans could be called "The Forgotten Generation." Current books and buyers' guides emphasize the coupes, cabriolets and SLs and, with the exception of the 300SEL 6.3s, ignore these magnificent and practical sedans, making them much less expensive than other classic Mercedes-Benz automobiles and thus even better for the beginning classic-car enthusiast.

Background

The W108-W109 series was developed to bring a larger and more contemporary style to the lineup of Mercedes-Benz sedans. Visibility is very good. Paul Bracq's styling remains timeless, and few people recognize the car as being a 50-year-old design. The trunks were larger, the wheels were 14 inch (instead of 13 inch), the engines were more powerful, and the driver and passenger amenities were more in line with cars of the 1960s than previous-generation Mercedes-Benz sedans. Four-wheel disc brakes were standard. Air conditioning was mounted under the dash, but was not known for being effective in temperatures above 85F. Seat belts were standard, although fitted with Kangol magnetic buckles that seem quirky by today's safety standards.

Virtually all vehicles coming to the United States had automatic transmissions; the 4-speed manual transmissions with a column-mounted or floor-mounted shifter was an option on all models except the 4.5- and 6.3-liter V-8s. A 5-speed manual transmission with a floor-mounted shift lever was available on the 300SE, 300SEL 3.0 and 2.8, 250SE, 280SE and 280SEL equipped with the inline six-cylinder engines.

Total production worldwide of the various W108-W109 models was 383,341 from 1965 to 1972. The range could be considered a success by the fact of that volume alone. This also means that there is a potentially large pool from which to select a pristine example. Remember the adage, "Always buy the best example you can find." In general, full restoration is always more costly than the ultimate value of these vehicles.

Why to buy a W108-W109

• Engineering and build quality were excellent. Safety features make the W108-W109 an exceptional family car for daily use.
• Styling is contemporary and classic at the same time.
• These models can comfortably haul five people and their "stuff" on trips.
• Parts (new, used, and remanufactured) are generally available for W108-W109 bodies, engines, drivetrains, etc.
• Air suspension on the W109 series offers a supple ride with great handling and control.
• The model range was built with a variety of engines, so you have many choices.

Why not to buy a W108-W109

• Sedans often suffer from neglected servicing and components that need rebuilding or replacement.
• Bosch D-Jetronic fuel-injection systems on 3.5- and 4.5-liter V-8 engines are expensive to repair or rebuild.
• Faulty steering boxes and automatic transmissions are expensive to replace.
• Fuel-system components (from fuel tanks to fuel pumps to carburetors to injection systems) may need rebuilding or replacement due to damage from ethanol fuel additives – particularly a risk for a car that has been stored for years.
• All W108-W109s require premium fuel, although unleaded fuel is not a problem because Mercedes-Benz used hardened valves and valve seats on all models by 1951.
• Automatic transmissions may shift harshly and must be properly serviced to assure longer life and smoother shifting.
• Door-lock systems, window regulators, window-channel materials and power-window switches may need to be rebuilt or replaced.

Checkpoints

• Chassis – Although the factory touted its "heavy slathering of plasticized undercoating," rust is always a major issue, especially with front frame rails and bumper supports because of their structural importance. In addition, floor pans, fenders, door rocker panels and doorsills need to be checked.
• Engine – Most of these lower-priced examples have been just "old cars" for a long time, purchased by people who might not have had the money or time to invest in engine maintenance. Engine bearings, camshafts, and other moving parts can suffer from postponed oil changes or oil with the improper lubricity classifications. Have the engine checked out thoroughly by an experienced Mercedes-Benz mechanic with the proper equipment to avoid expensive surprises that can double or triple the price you pay for the car. Pay particular attention to the fuel system, as noted below.
• Suspension linkages – These cars have lubrication points throughout the suspension and lack of regular maintenance can allow the grease to solidify into a concrete-like consistency, causing damage to lower control arms, suspension links, kingpins and dried-out bushings that need to be replaced. The early cars had a hydraulic compensator on the rear suspension. If it fails, it can also damage axle boots.
• Air suspension – Repairing the air suspension system of a neglected car may be very costly. Air suspension on all 109 models requires regular maintenance and the use of methanol-based antifreeze to avoid water in the air lines. Check for damage to the air valves, air lines, pump and air bags. A well-maintained air suspension should hold air without leaking and stay inflated for two weeks. The 109 series with air suspension are: 300SEL; 300SEL 3.5; 300SEL 4.5; 300SEL 6.3. The 280SELs were not available with air suspension.
• Differential – Bearing noise and gear-lash adjustments are the most likely culprits here. Bearings may need to be replaced. The 6.3 models are vulnerable to differential wear and stripped pinion gears because of overly enthusiastic driving. "But, Dad, the 6.3 has so much torque! I had to test its performance."
• Interior – Heater-blower motors and bronze bearings are inaccessible and quite expensive to replace. Heater-control levers can be easily replaced, although the underlying problem of poor access to lubricate the controls and cables is an issue for all Mercedes-Benz vehicles of this vintage. Power-window switches may need to be rebuilt (see article in The Star, July-August 2008, pp. 76-80). M-B Tex (bonded vinyl) is nearly indestructible, but back-seat upholstery may dry out from sun exposure coming in the back window. Carpeting wears out, although complete color-matched kits are available from several sources. The woodwork on the dash is not as finely finished as in other models and may need to be refinished or replaced.
• Gearbox – Automatic transmissions are fairly durable, but often need a rebuild kit for vacuum modulators. These are fairly basic, mechanically operated units that are durable if serviced regularly. For the column-shift, check the cable-driven shift indicator for adjustment or replacement and general wear in the shift linkages and bushings to the transmission.
• Fuel System (carburetors or fuel injection) – Poorly maintained carburetors and fuel-injection system necessitate rebuilding, although the basic components are quite durable and don't often need to be replaced.
• Power Steering – Power-steering pumps and reservoirs may need rebuilding and hoses replaced.
• History – Get as much information as you can about the vehicle you are interested in from the seller, including history of maintenance as far back as you can get it. These vehicles are well engineered and quite durable, but the 6-cylinder engines will likely need a rebuild around 200,000 miles, while V-8 engines are probably good for 300,000 miles.
  
  

Finally

A well-chosen example of any of the many models from the W108-W109 range can offer the canny Mercedes-Benz enthusiast that rarest of opportunities in today's heavily scrutinized classic-car marketplace: an elegant, timeless example of a high-quality automobile from a seminal period in the company's history available at a comparatively modest price.