Watching some of these videos that are posted where the engines have been stuck in the snow for days, how much damage was done to these?
With all the valves, piping, boiler tubes and even the tender freezing up it must have been months before these were put back in operation.
Being a plumber and replacing frozen and broken pipes in houses, it doesn't take more then a teaspoon of water in a valve to cause problems. These engines and tenders had thousands of gallons of water on them.