I went to the Roseville yard last weekend, and this pair of GE's stopped right in front of me. While I watched, the engineer started one of them. What an enormous feeling of power! But my question is about the MU cables. I thought the so-called "multi unit" cables were necessary to run multiple engines. But the MU cables on these two were obviously not connected to each other. What exactly are the MU cables for?
The MU cable is for running engines together. However, in a yard, you can just drag an engine around without hooking them up. If you'll look closely, none of the air hoses are hooked up. The engine had probably been sitting awhile and the air had all bled away. No need to hook the air or anything up. Sometimes, when the brakes still have air in them, you can just hook up the train air and set up the control stand so you can control the brakes from the engine you're running from. Less work to do.
This is purely a guess, but compressed air gets very hot and perhaps these finned bodies help to cool the and to automatically drain condensate from the lines.