The fans in the F40 are in the same location they would be in, on a Geep 40. Directly above the radiators. You can't see them, because they are a sealed enclosure, so all the air they pull though them, enters only through the shutters, and passes directly through the radiators. They were above the air compressor, and there are squared oval access hatches, with little metal retaining clips, that allow you to examine the underside of the radiators, for leaks, etc. If the unit has DB's there is another fan centered above the diesel, and it too will be shrouded to ensure all air pulls through the grids. The fans can actually operate at different speeds, and independent of each other, as cooling needs change. The shutters also play part in this, closing until the loco is hot enough to need actual forced air cooling. From the cab, the DB's are the easiest to hear, and understand, as they step their way up and down, through the differing speeds in and out of extended range. The newer cooling fans run the same way, and some of them do make a different kind of "howling" sound, as opposed the the older (and cooler sounding) whine that had a siren like quality to them.
BTW, Dan, the cooling fans on EMD's, that you mentioned, are like all EMD's, except for the early "F" series, and the SW/NW/SC/MP series switchers. They have electrically driven fans. Lot's of Alcos, GE's and Baldwins had engine driven fans, either from a driveshaft/drivebelt arrangement, or through a gearbox that directed horizontal rotation to vertical rotation to directly drive the fan. EMD has always utilized the electrical cooling fans, once it built locos other than those mentioned above. Hope this helped......
