Un bazou doesn't mean a car, it's a slang word that means jalopy. In France French, one would say une guimbarde, and I suspect lots of Canadian French speakers wouldn't understand that word. Slang words tend to differ a lot from country to country, no matter the language. A translation service that translates car to bazou or guimbarde is broken, but this has nothing to do with Canadian vs. France French.
Or tell them on your gardening website to fill a chaudière to water their garden.