Hello! I'm seeking for information about diesel locomotives.

So i'm studying automotive engineering, and one of courses is about locomotives. It's basically basics of locomotives - types, what they consist of, and so on. But one of assignment was to do a report about locomotive construction - in my case - about cooling system of diesel locomotive, types, how they works, schemes and so on. So i'm kinda struggling to find any e-book in english language about them - maybe someone knows/haves an e-book about them? Because in my country where i live, even in my native language practically there is no books about them, even in libraries. I would be very thankful if someone has an ebook or some forum where i might get an info, or just something to grab on..

There is a superb WWWebsite of railroad images, "Fallen Flags,"
http://www.rr-fallenflags.org/
which has a section of "Operators Manuals". This has (some in HTML and some as PDF) a number of operators manuals and some maintenance manuals for various sorts of diesel locomotives: the maintenance manuals would give at least some information about the cooling systems.
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Basically, the cooling system consists of a radiator and fans, as in other applications of internal combustion engines. Details (e.g. are the fans direct-driven from the engine or electric, etc etc etc) vary between locomotive builders, and between models from a single locomotive builder. On modern (post about 1993) locomotives it gets even more complicated, with separate radiators for the basic engine cooling water and for engine lubrication oil ("split cooling").