I know there have been a couple of threads on the subject but wanted to add my experiences so far with this issue. I have 20+ years exp wrenching everything from cars to aircraft to combines, but this is my first foray into the 4.6L. I started losing coolant a while ago, slowly at first then increasing to about a gallon over 4-5k miles. Cooling system held pressure losing only 2 PSI overnight, cylinder leak down test showed loss past the rings but nothing into the coolant, compression tests OK, no obvious coolant when draining the oil, no external evidence of leak, but it continues to go away. The engine has 132,000 miles on it. I decided to do some exploration to see what I could find. I pulled the intake and found a small crack in the plastic where the aluminum crossover tube attaches. Notice the line parallel to the end of my thumb. Here it is with a light under it, you can see it goes all the way through. And evidence of liquid in the valley Thinking I had found my culprit, I decided to go ahead and reseal a leaking valve cover and replace the timing chains, etc due to a rattle at start up. When I pulled the valve covers I found this. This seems like an excessive amount of goo to attribute solely to condensation, unless the crankcase vent on this engine is really that bad. Now I am not convinced the intake was my sole problem. I pondering if I should pull the heads anyway or go the extra mile and pull the engine to inspect bearings, etc. Anyone else been down this road recently? I recently replaced the differential due to howling and clutch chatter with a reman unit from Zumbrota Bearing and Gear (Great outfit) and rebuilt the tranny after the overdrive planet exploded, so I really am not ready to ditch this vehicle yet..... UPDATE: After pressurizing and letting set overnight again, coolant drained out of the oil pan. The engine is now out on the stand for inspection and repair.