CAT 420D Coolant Leak

As I was moving snow a couple of days ago, I noticed red stains appearing under the front of the machine (as I was backing up). Although the water temperature gauge continues to indicate a normal reading, I also started to notice a bit of a steam-like odor. After parking the machine, I lifted the hood and immediately noticed liquid spatters on top of the top radiator hose and a red liquid on the front of the (yellow) engine. After the engine cooled down, I put (2) gallons of red coolant into the radiator -- without filling it up. Obviously, the machine is leaking red coolant from somewhere?

We're going through a Siberian cold air front here, at the moment, so I haven't been able to take anything apart in an effort to localize the leak. I have performed a visual inspection, though, and the hoses look good. The machine is a 2002 model (just under 3,000 operating hours) with a serial number ending in FDP 08XXX. At this point, I'm simply looking for thoughts on where I might start troubleshooting this issue.

Thanks very much you for your time... :usa

P.S. Any thoughts on a good source for a service manual would be much appreciated, as well.

CAT 420D Coolant Leak