I'v used steam cleaners before, when I'm working on old cars with years of grime. They've always been big units, that are a combination boiler and power washer. Something like this: Hotsy Hot Water Pressure Washers | Corporate Site
Here's some reviews of your machine: McCulloch MC-1275 Review
That kind of steamer is for cleaner bathrooms, carpets, etc. Strictly light duty and in-home stuff. I can't imagine you'de get amazing results on old car parts.
I have a pressure washer, and I just hook it up to the hot water.
Fortunatly, I have a large sink in my garage, with hot and cold running water. I clean parts with Simple Green and Brillo pads. Extremly effective. The hotter the water is, the better it will clean. I have also put parts in the dishwasher for a final cleaning before paint. That works especially well for used alum parts, to get rid oil that's below the surface.