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"Watch where you're going!"
"Diesels are dangerous! You always cause accidents!
— Diesel and Percy

Bubbling Boiler is a magazine story.


Percy is rolling slowly across the yard when his wheels slip on some Diesel oil and slides into a set of buffers. Diesel teases him and Percy accuses him of always causing accidents. Meanwhile, Emily pulls into the platform with shiny carriages as the Mayor arrives to catch her train. As the Fat Controller greets him, a strange bubbling noise starts coming from Percy's vicinity. Diesel teases him by calling him "bubbling boiler" making Percy furious.

The Fat Controller sends Percy to the works to have his boiler cleaned out. Soon after, the gurgling noise starts again. Soapy bubbles emerge around the engines and it becomes apparent that the noise is not coming from Percy. Suddenly, a man runs into the station. It is the owner of the launderette next door. He explains that too much soap powder had been put into the machines. He goes on to explain that the soapy water had filled the drains. Percy was happy that the engines could not call him "bubbling boiler" any more and the engines will soon be clean in no time.