In order to take advantage of superheated steam technology that was just emerging, an example of the S 3 was converted in 1898 to test this technology. It was the world's first express locomotive of this type and the flame tube superheater used was the first variant of the superheater to be used. This consisted of a 445 mm thick tube, which was arranged in the boiler barrel and contained the tube bundle for superheating the steam.
Since this first construction was not yet completely convincing, but showed a very promising approach, two more examples were converted over the next two years. These had the superheater in the smoke box and ultimately led to the production engines of the S 4.
In 1902, production of these engines began, which in reality were completely new designs. Although they weighed the same as the S 3, the power could be increased by about a third. While the predecessor could pull 320 tonnes at 75 km/h on the level, it was now 80 km/h with 420 tonnes. In tests with only three cars, an S 4 was even able to reach 136 km/h. From 1906, a smoke tube superheater was finally used, which later became state-of-the-art.
![Prototype with smokebox superheater](./data/photos/preussische_S4_2.jpg)
Prototype with smokebox superheater
Die Lokomotive, June 1910
Nevertheless, production was ended in 1909 after just 104 units, since the underlying design was already outdated and the S 6 was a much more modern locomotive on offer. As with other, older locomotives, the Reichsbahn took over significantly fewer locomotives in 1925 than had been envisaged in the original renumbering plan a few years earlier. The number had already halved about five years after the end of production, so that the Reichsbahn just planned 44 engines as 13 501 to 13 544. In the end, just four locomotives were taken over, which had also disappeared by 1927.