The group KHD-Deutz has produced a lot of liquid cooled diesels but I've never seen them offered in a tractor. We used quite a few of their V-16s marine diesels back some years ago. Their air-cooled diesels have been used in many a hovercraft too. We even tried using them for generators and lift fans on surface effect ships. Biggest "problem" with them is they are very noisy compared to water-cooled options.
