Steamer Trucks

We were driving down the road the other day and Magnum asked me if there was a steamer truck in front of us. I couldn't figure out what he was talking about, so I said no. Kannon chimed in with a "yes it is!" There was an eighteen-wheeler a couple of cars in front of us and I asked if that's what they were talking about. They said it was and when I asked why they called it a steamer truck they said because they go "ttssshhhhhhhh!" It's so funny how their little minds work.