2004 Dodge Dakota 3.7 V6 Engine Rattle?

My 04 Dakota developed a serious rattle sound under the hood today. I am not very mechanical, but when I looked under the hood, it seemed the hub of the fan seemed to wobble when the noise happened. There was also some brown water like fluid that seemed to be flung around inside the engine compartment. It was not oil, too thin, the transmission fluid levels were good, brake fluid was good, and it did not smell of gasoline. The truck seems to be running fine other than this noise and the CEL light did come on, but I don't have the code. Any idea what the problem could be before I spend a fortune at the mechanics for diagnostics?