Dustodustrider

I am trying to figure out what the gap is around the top of the spark tube in this photo. I changed the spark plugs and boots 1 at a time starting at #1 and everything was fine until I removed #8 and saw a piece of rubber like an O-ring come up with the coil and boot. It looks like some sort of dust seal .
I cant figure out if I am looking at where a spark plug tube meets a flange in the intake manifold ?
How critical is this seal point ?


BTW, the job went smooth, some plugs had very minor corrosion outside , but the electrodes all were slightly eroded and gaps worn open, nice chocolate milk brown color, but it was quite a carbon insulated gap for a spark to jump.
I also cleaned the electronic throttle body and at first it ran kind of odd (slow drop idle hunt and unusual shift points ), but I came back and remembered to reset the TPS point as directed in the (HAT TIP) Makuloco vid but overlooked it. After reset it runs better than it ever has since I have had the truck. The dash calculator read 17.6 MPG at one point then settled back to 16.8. I have never seen it read that high. better acceleration also. I was hesitant to "fix what aint broke" because it was running great before, but I got a misfire on cyl 1 fixed it by cleaning the boot but figured it was a warning and changed all the plugs and boots

Dustodustrider

The mystery continues ,
there are hundreds of videos on youtube about changing spark plugs but not one peep about what these O-rings are for and where the empty space behind leads to.
Lots of mechanics blowing compressed air at the O-rings in a cavalier manner, but no reference to them.
I searched for an hour for diagrams still nothing
I could buy a $100 service manual but that is no guarantee either
77 views so far but no answers

Dustodustrider

OK , nevermind, I found the answer here in a cutaway view of the head (after searching for hours) mine is slighly different because I have a 2010 3v 5.4 :
evidently the recess leads to a redundant chamber between the head casting and interference fit spark tube.
The purpose of the O-ring must be to stop water from getting in there and causing corrosion

might want to be careful blowing around in there to avoid blowing out those O-rings

Snickernutz

same thing happened to me when i pulled my heads to extract the broken plugs. I cleaned the heads and the tube seals blew out. I was told it is just a dust seal and to remedy this, try to push some high temp rtv around the mating surface of the head and tube.