Abstract: There is disclosed a method of cleaning a liquid hydrocarbon-cooled bipropellant rocket engine. In an embodiment, method includes heating the engine to a temperature. The method includes applying ozone for a period of time. The method includes determining the temperature and the period of time are each sufficient to remove carbonaceous deposits. In another embodiment, the method may further include thermally imaging the heat transfer surfaces. There is disclosed apparatus for cleaning a liquid hydrocarbon-cooled bipropellant rocket engine. In one embodiment, the apparatus includes a heater, an ozone source, and a thermal camera. Other embodiments are also disclosed.