Once upon a time I knew of an engine that was known as a poor steamer. Always steamed poorly in the summer. Then, it steamed better in the winter. Next summer, it'd steam poorly again.
Well, so, the CMO decided to rebuild the cab of that poor steamer to improve ventilation in the summer. Wouldn't you know, she started steaming better again.
(Next poor steamer story will have to do with the fireman who didn't like that "cheap" Pochantas coal. That'll be followed by another story about the other fireman who'd clinker it up on anything but that "cheap" coal.)