Head Rebuild - Mystery bolt ID

[JeepMonkey]

So I put a new head on my 2001 TJ, 4.0 this weekend and I have a mystery threaded hole on the rear of the new head that does not exist on the original. Can someone please help me identify it? I've attached a picture of one I found online with something in that hole, but I don't know what it is. The bolt with the arrow pointing to it is the one I'm trying to figure out.

P.S......I realize there is quite a great opportunity for "that's what she said" jokes, so let me have your best shot!

 

[Jester32]

That's the coolant temp sensor for a Guage. Not the PCM. Is this an older head. Say off a Cherokee or yj?

 

[JeepMonkey]

That's the coolant temp sensor for a Guage. Not the PCM. Is this an older head. Say off a Cherokee or yj?

It's a brand new head. I think they must've drilled that because it is interchangeable with the older models as well. I confirmed with the original photos owner that it is the temp sending unit.

I think instead of finding a plug to fit it, I'm just going to the junk yard and pull one off an older model to plug the hole with.....at least that way I don't have to worry about cross threading.

 

[Jester32]

Ya. That will work. Is it a blind hole or is it into coolant.

 

[JeepMonkey]

Ya. That will work. Is it a blind hole or is it into coolant.

I'm not sure what you mean by "blind", but i'm assuming that is into the coolant as there is steam coming out of the hole.

 

[Jester32]

Ok ya lol. Blind hole is a hole with a bottom. But that is obviously not blind lol.