The Mercedes-Benz W 108 is a timeless car. Hard to believe that this luxury-class model series was launched a full 50 years ago. Its design was created by the then Mercedes-Benz stylist Paul Bracq. In terms of comfort and spaciousness, a W 108 still sets standards. Alongside the models with normal wheelbase, which were only available with a steel suspension, Mercedes-Benz also offered the long-wheelbase SEL models with the option of air suspension. Even more lavishly appointed, they formed a model series in their own right, with the designation W 109.
Potential buyers of a W 108 should be sure to take a very close look at the bodywork. Poorly finished repairs and rust damage can incur costly repair work. The door sills and the rear part of the longitudinal member, which forms an arc over the rear axle, should if possible be rust-free. Holes in the inner sills (lift the carpet!) or in the door or hood frames, are all indications that the rust attack is already well advanced. Replacing chrome trim and fenders can be very expensive.
A look at the underbody is also essential. The front cross members are frequently in a state of disintegration. Corrosion is also commonly found in the wheel arch areas and around the A-pillars. Rust may also be festering in the engine compartment. The cavity above the headlamps, for example, is one of the critical zones. At the rear, the floor of the trunk and the spare wheel recess are vulnerable spots. If the W 108 you are looking at has a sliding roof, it may also be worth looking at the frame: Any rust here will involve extremely expensive repairs.
As far as the engines are concerned, the 2.5-litre versions (photo) have a reputation for not being able to cope with full power. But if you find a well-kept 2.5-litre example you can still invest with confidence since, as classic models, these cars are normally only driven with extreme care. The aluminium three-litre unit in the 300 SE can incur high repair costs if damaged. 280 S/SE and 280 SE 3.5, on the other hand, offer impressive longevity. Both manual and automatic transmissions are generally considered to be robust. A particularly rare feature in the 300 SE/SEL is the five-speed manual transmission that was offered from as early as 1966.
A test drive is important. As soon as you get into the car, consider the condition of its interior. Not every component, nor every upholstery fabric, is necessarily easy to replace. There should be no clouds of smoke from the exhaust when cold-starting the engine of your chosen model. Nor should there be any dark swathes emerging once the car is moving. If this is the case, you should commission a compression test. When driving, the oil pressure indicator should not fall below 3 bar.
The W 108 is fitted with a single-joint swing-axle suspension. Regular lubrication of the axles is absolutely essential. Another critical point is the mountings for the transverse control arms. These must be intact, or they may break away during driving. The hydropneumatic compensating spring (mounted transversely on the rear axle) often leaks with age. However, we do not advise fitting a cheaper steel compensating spring: as there is no manufacturer’s approval for this component, this could void the operating permit.
And finally a quick word of advice on availability: W 108 models are easy enough to find on the classic car market. A lot of the vehicles available, however, are graded with a condition score of 3. When looking for a good example, potential buyers should therefore exercise patience. On the plus side, no dramatic jumps in price are to be feared in the foreseeable future.
Checklist and definition of condition scores.