Nothing on your bike has rubber o-rings like a motorcycle chain. A little home steam cleaner like you see on infomercials probably wouldn't hurt anything. Some kind of industrial high-pressure steam weapon might be a problem if you point it at bearings in your hubs/headset/bottom bracket.

We all wash our bikes with water and they don't rust to pieces. It is a good idea to treat the inside of a steel frame with something but unless you leave it submerged even an untreated frame should stand up to many years of occasional washings.