Cars Mercedes-Benz 300 Cabriolet D

Published on January 1st, 2023 | by Daniel Sherman Fernandez


Mercedes-Benz 300 Cabriolet D Remains A True Statesman’s Ride

This 300 Cabriolet delivered more than luxury iconic British marques.

It was the most expensive luxury car of its day, twice as much as the 300SL and American luxury cars of the day. It did not have the full appeal of a Rolls-Royce, but its delivered advanced engineering, comfort and luxury appointments to match any Rolls-Royce and Bentley.

Equally important, it was the model that returned Mercedes-Benz to its pre-war international clientele.

Hence this was a car of the rich and famous including the Aga Kahn, the Shah of Iran, King Gustav of Sweden, Frank Lloyd Wright, Gary Cooper, Yul Brenner, Maria Callas, Clark Gable and even the infamous Bing Crosby.

PRESS RELEASE: After the Second World War, the benchmarks had changed in Germany and Western Europe. People were suffering greater hardship, their needs were existential, their standards more modest, the newly elected Federal government in West Germany was closer to the people and democratic.

The Federal President and the Federal Chancellor initially used cars merely as a mode of transport. They were cars like the the Pullman saloons and cabriolets from the Mercedes-Benz, Horch and Maybach SW 38 brands from pre-war times, and the Governing Mayor of Berlin, Luise Schröder, used a Model 170 V as her official car.

At first everyone at Daimler-Benz had other things to worry about than thinking about a remake or new design of the ‘Super Mercedes’. The overall economic situation was gloomy, characterized by the rapid collapse of the ruined Reichsmark.

Mercedes-Benz 300 Cabriolet D

Wilhelm Haspel called a meeting on 22 December 1947 with the aim of discussing plans for a sports and representative car, which for a time he was not Chairman of the Board of Management at Daimler AG due to de-nazification, and it was not until 1 January 1948 that he took on this position again.

The aim of the meeting was to decide on a range of vehicles also suitable for export – even in such dark economic times, Haspel recognized the necessity for Mercedes-Benz cars with the appropriate charisma in the luxury segment: ‘But what is missing is a vehicle that gold-plates the name Mercedes-Benz again.’

Another year and a half would pass. Initially priority was given to the Model 170 S (W 136 III, later W 136 IV), which Daimler-Benz brought out in 1949.

Before the war it had originally been earmarked as the successor to the Model 170 V (W 136), and for two years it now assumed the role of the later S-Class in the Federal Republic of Germany in terms of price and social status.

The two-seater Cabriolet A even became the country’s most expensive car. In 1951, the Model 220 (W 187) was launched, and it, too, was one of the S-Class’s forerunners.

Against this background, the Model 300 (W 186 II) which was unveiled at the same time was seen as a superlative-class car back then, something that was reflected in its price and performance as well as its appearance.

But in the meantime the development department took several approaches when it came to creating a vehicle that gold-plated the name Mercedes-Benz again. In order to keep costs and new invest­ments to a minimum in view of the difficulties involved in the procurement of machinery, existing stock was used up.

Where the chassis and the bodies were concerned this meant the Model 230 (W 153) with the all-steel body from Daimler-Benz which had come out shortly before the war, plus the corresponding chassis with an X-type pipe with a wheelbase of 3050 millimetres.

When it came to the engines the production units for the 2.6 litre M 159 engine had survived the bombings to such an extent that they could be built up again. This resulted in no less than 9004 units of this engine being produced between 1941 and 1944.

Although originally intended for passenger cars, they were all installed in the 1.5-tonne L 301 model, which had carved out a career for itself as a small fire-fighting vehicle, and as a bucket-seat car.

This engine had a hemispherical combustion chamber with V-shaped overhead valves, which were operated by the low-mounted camshaft via tappets. The first deliberations regarding the construction of a more representative vehicle were made on the basis of this M 159 and the model series W 153.

To begin with it was given the model series designation W 182 and was intended to have a displacement of 2.6 litres. In order to take into account the increasing vehicle weight, in 1949/1950 the engine was given a series of higher displacements in rapid succession: firstly 2.8 litres and finally 3.0 litres, with various model variant designations to match.

The engine derived from the M 159 was known as the M 182, and whilst it still had a crankshaft with four bearings and a displace­ment of 2.6 litres, it already boasted a modified cylinder head with larger valves.

This was where engine developer Wolf Dieter Bensinger fell back on a design list that had been put together as a stop-gap measure, and this resulted in the characteristic oblique contact surface between the cylinder head and the cylinder block for the engine which was now called the M 186 I and for the variant derived from it.

It was in order to take over as many production machines as possible from the manufacturing of the M 159 on the one hand, and also to create room for larger valves in the cylinder head on the other, that Bensinger hit upon the idea of the oblique section, which provided the larger area that was needed.

Along with the increase in displacement the crankshaft was converted over from four to seven main bearings. This engine with the internal designation M 186 I still had overhead valves operated via tappets, but that changed with the advent of the M 186 II, which operated the valves via an overhead camshaft.

It was not until a good year before the vehicle presentation at the International Motor Show in Frankfurt am Main (IAA) in 1951 that chief engineer Fritz Nallinger told his colleague Karl C. Müller: ‘The results of work involving the M 186/II engine with an overhead camshaft have now reached such a stage that this design can be described as promising.

Therefore, I would ask you only to firmly plan in the machines which are used for the 186/II design and to set aside the machines which are additionally needed for 186/I.’

Somewhat confusingly, the engine described at the testing stage as the M 186 II was later given the designation M 186 I or just M 186. Meanwhile the first design of the Model 300 always bore the model series designation W 186 II.

On 27 March 1950, in a report about the Geneva Motor Show, Nallinger also informed his Board of Management colleagues about the development status of what was classified internally as the ‘Group B car’, the Model 300: ‘The cylinder volume has been increased to 3 l, the control shaft moved upwards into the head.

This has resulted in the following advantages: better governing of the engine speeds with regard to valve control, so that engine speeds resulting in favourable valve-time cross sections are achieved with the steeply rising cam shape. This means that with the 3 l engine with the normal carburettor engine and intake manifold configurations 115 hp is achieved.’

A surprise came in the form of the newly designed three-litre M 186 engine with an overhead camshaft and 115 hp (85 kW) at 4600 rpm.

Mercedes-Benz 300 Cabriolet D

With a maximum speed stopped in tests by specialist journals at 158 km/h (‘auto motor und sport’), 160 km/h (‘Automobil Revue’, Bern) and 164 km/h (‘ Motor Rundschau’ and ‘The Autocar’) it is Germany’s fastest car up until the unveiling of the Model 300 S (W 188) in October 1951, the latter being nothing other than the sporty two-door variant of the Model 300.

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