wpartlow, if the leak is on the back corner of the block it can be 1 of 2 things. The more likely thing is the coolant hoses that go into the firewall tend to leak, leading to a failure of the #4 COP. You can remove the hose connections and replace an o-ring inside the connection and that should fix your problem there.
If the leak is coming from lower, then it is very possible that your head gasket is shot. There has been a significant number of problems with the head gaskets in this corner of the block. Granted, they normally manifest themselves as an oil leak there, not as a coolant leak. But, it could be possible. As for replacing the gasket, plan on about 12 hours of wrenching. You have to pretty much take off the entire front of the engine to get to the timing chain so you can pull the head. You can also plan on about $300 in parts (top end rebuild kit and a box of head bolts at a minimum). You can possibly get off cheaper if you only get the head gasket, but then you have to hope the rest of the gaskets are good. So, your call. The single head gasket and bolts will set you back about $150. If you need more info, let me know. I have pulled both heads on my truck. So, all too familiar with it. THe hardest part of the job is getting the timing set back up correctly. Once you know what to look for, it is fairly easy. But, if you follow the instructions on the Ford Service CD, it will mess you up. TRUST ME!!!!!
