Interesting incident on oil burner

I was doing a pretty intense cabride on a loco which will remain nameless to protect whatever and we kept hearing this thumping noise from the boiler....I thought this can;'t be good, but kept on shooting video anyway. The crew looked at each other and couldn't figure out the problem. They sanded the flues, and checked out everything else. We finally stopped and did some more inspecting. They said this had only happened once before and they couldn't remember what was causing it. Finally they figured it out after they stopped. There is an oil heating unit on the tender, that preheats the oil before it goes through the atomizer into the firebox, and the oil was too hot, essentially vaporizing before it got to the firebox or something like that. Once they got the heater regulated everything was fine. I still have some of this on tape, but out of courtesy to the crews it has never made it for public consumption.
We also went into emergency on that same cab ride, due to a broken air hose. They must have known I was going to be doing charters on the C&TS someday, and have the selfproclaimed nickname "Snakebit Enterprises"?
Greg Scholl
(another fun story from the days of yore!)