Eric, the 84A and 84B, which became the 207 and 208, were unique in that they had an auxilary water tank for the steam generators. That piping was the fill pipe for the auxilary water tank which was mounted inside the carbody near the roof. In bitter cold weather the Monon liked to use these engines whenever possibile because of the extra water supply.
Another unique feature of these two units were regular air hose that were mounted vertically on each side of the rear door, glad hand up, but they were used for water, not air. When these were coupled between units, and the valves opened, they would equalize the steam generator water between the two units so one wouldn't run out of water before the other. Sorry, I don't have a picture of the rear door on either of these units that show those hoses. / Ron
PS, I was one of several firemen at McDoel that was qualified to hostle Monon passenger units at 10th. St. depot in Louisville, and we had to fuel the engines and check all the steam generator stuff when the train arrived in the evening, and again before it left the next morning. The regular hostler, Clarence "Stony" Stone was a fixture on the job, but we filled his vacations and vacancys from the McDoel board.
