CR 6309 near Benny on May 22, 1977

Note the yellow stain under the radiator on the trailing SD45.  That's dried chromate.  Chromate was the preferred water treatment for the cooling system then.  It was yellow.  SD45's radiators were notorious leakers.  You'd often see yellow icicles in winter - a problem later solved with mechanically bonded radiator cores instead of solder.