Hi,
I am working on a 2005 Expedition 4x4 5.4l 3valve. Has 120K miles on it. The check engine light came on, scanned it, and came up with a cylinder #4 misfire fault code. When I pulled the coil out of cylinder #4, I noticed that down around the bottom of it, there was what looked like some coolant on the boot. This really concerns me. I swapped the coil to another cylinder to see if the code moves, but if it does, that really may not be the root of the problem if coolant is getting in to that spark plug hole. I cannot find any leaking heater hoses or other ways of coolant getting in there externally so im thinking cracked head??? I sure hope not. Havent had time to run it long enough to see if the fault code moves or not, but I realize that the real issue here is why is there coolant on that coil boot? Any ideas?
Everything is bone dry on top of the engine around the coil. Its only wet down in there where the boot is.

 

Well this morning the check engine light came back on and I scanned it again to see if the misfire moved cylinders. It did not. Still misfiring on cylinder #4. So this tells me what I thought last night, that the coil is probly not the issue. It's the moisture thats getting in that spark plug hole.
This does not look good.

 

Possible leaking intake manifold, either cracked manifold or bad gasket.

 

Yea, from what i've been reading that is the likely cause. I'll check when I get time.

 

Do the later models have the coolant line that runs right above #4? I know the 97 - 02 models do and that can leak down on the coil pack.

 

Yes the heater hoses go right over the number 4 coil on mine but they, nor their connections are leaking. Bone dry in fact. Looking at the top of the engine there is not a single wet spot anywhere on it. The ONLY place thats wet is down in the spark plug hole. I understand intake leaks can cause coolant to get into the hole on some of these engines. What i cant figure out is, on my engine, the intake runners come in to the inside of the spark plug hole and the cylinder head has a lip on it that would keep coolant from running down in the hole. So how could that gasket being bad let coolant in there?
Is the spark plug hole one solid piece all the way down to the threads at the spark plug? If so, the only thing I can think of is a crack. Right??
I can see how the older style aluminum manifold could leak coolant into the holes as, i think, it's runners come in on top of the cylinder head right next to the holes. But with my plastic one, like i say, it comes in to the inside of the head with that lip separating the hole from the runner. Heres what my intake looks like

 

Justing, I PM'd you -- did you ever get this fixed??

 

Justing, you there? Can anybody else help??

https://www.ford-trucks.com/forums/1...and-p0300.html

 

Justin,
You never said you changed the #4 plug after changing coil paks. If you haven't changed the plug, I would do that and not worry too much about the coolant unless it really starts to fill the plug hole. I've seen many cases of antifreeze on the plug but with dielectric grease around the contact area, you can drive for many miles without issue. (Vacuum out antifreeze before removing plug)
You will know when it's time to replace the intake gasket with excessive leaking.