Wilson's Icy Escapade - S2.E18

On an icy winter's day, Wilson and Koko are sent out to sand the tracks in the mountains. They take a short cut through the ice cave. Koko does everything properly, but Wilson doesn't keep his mind on the job, as he has fun exploring. He doesn't realise that an icicle has fallen into his sand wagon, wetting the sand and rendering it useless. He's stuck! He figures out a way to dry the sand by using the heat from his engine and makes it back to the depot - after finishing his job, of course!