What's this hole in my head?

[azmx74]

2003 Expedition 4.6, I'm chasing a P0171 after doing the usual things. I removed the intake manifold after seeing oil/oily residue in the back passenger side on & around the plenum. Can anyone tell me what the hole in the back of the bank 1 (pass. side) head is? In the first picture, it's between the two bolt holes. The manifold only bolts to the left one of those holes, and cuts the mystery hole in half (second picture). Third picture shows the gasket there where the covered to uncovered part is clear. Should this hole be plugged? or connected to someting? Is it the source of the oil and/or possibly the vacuum leak? Thanks for any help!

Photo1: what's this hole:


Photo2: Intake manifold:


Photo3: gasket back there:

 

[Stoned06]

Are you sure those are stock manifolds? I would assume the gasket would be solid over that hole if it weren't needed.

 

[azmx74]

Are you sure those are stock manifolds? I would assume the gasket would be solid over that hole if it weren't needed.

I thought that might be it... in fact I hoped that was it so that it would explain and solve it. But looking at detailed pics of a new Dorman manifold, it has the 45 degree slant in back just like mine, so it would also uncover half of the hole. Looking at new manifolds from other models with the 4.6, like a Crown Vic, the manifold does have some sort of vent over that hole. I found a pic here showing the rear of a pulled 4.6 from an '04, and I can make out the slant and half-covered hole in back too, so maybe it's correct like that? But in that pic there's no oil deposits and I might be able to just make out a plug there where i have a hole. One possibility I'm looking at is if a PO had swapped another 4.6 from another vehicle in there, and didn't plug it the hole?

 

[purple_50]

That is the stock set-up. The heads are interchangeable from left to right and if you look at the front of the left head you will see the same hole only it is used for coolant passage IIRC. They just install galley plugs in the back of the head depending on what side the head goes on, that way they make one part to cover both sides instead of 2 separate castings. That hole remains open and doesn't affect anything on the right side. The gaskets are also interchangeable from left to right so they will be identical too. That hole isn't the source of your vacuum and/or oil leak. The gaskets themselves could be your vacuum leak as they are good for that, or check the vacuum lines and hoses as well.

 

[azmx74]

Thanks purple_50. I saw where the gasket might be leaking, but that hole just looked too gaping to pass up. I'll button it up and hope it's fixed!