I have a 04 excursion with the 5.4l 2 valve modular engine. Has around 163000 miles. I've been losing coolant but I can't find where. The oil is good. No milky color. I've recently replaced the intake manifold because the old one developed a Crack in one of the cooling ports. This engine has never over heated. It warms up to 190* and stays there while driving. The top radiator hose becomes very hard while it is running. I can fill the expansion tank to the full cold level, drive it which the heater core has a gurgling sound, let it sit over night then have to add more coolant. I did find water coming out of the exhaust so I believe the coolant is going this route. I'm also chasing the dreaded p0304 and p0316 misfire codes. Can't find anything wrong with the #4 spark plug, coil or wiring. Is this a possible blown head gasket?

 

With fairly consistent coolant loss, all be it minimal....I would test the coolant for Hydrocarbons ( exhaust gases). You should be able to find these test kits at most any reputable parts stores.

If the test comes back positive for exhaust gases, then , YES it pretty much confirms a weak head gasket.

If not.... then. you most likely have a leaking the heater core and or its associated plumbing. Considering that you have a #4 cylinder misfire. I'm gonna hazard the guess that the heater core hose is weeping on to that #4 COP (Coil On Plug)

 

A cracked heater bypass valve is a common cause for leaks in that area.
Is there any way the intake could leak coolant into an intake runner since it was recently changed?