Never had mine apart but is that a groove for an O-ring ? Or for the clip.
Maybe an O-ring goes on the metal part. Look in the receiving end of the block for tapering where an O-ring would seat.
It's got to have something that seals it since it's a hydro pressure line.

EDIT. Adainc. Where is part #23 ? Is something missing ?

 

I think the bleeder threw me off. Well, we have a diagram now

 

I think the OP may be missing Part #23.

 

That is just the sleeve that the nipple sits in, and it is present


You may be onto something with the missing O-ring. Other vehicles(Saab, for one) use this same sleeve, around a pipe with an O-ring.


But I can't find a pic of the part in this HHR configuration.

 

By Jove, I think I've got it!!!
https://www.cobaltss.net/forums/prob...p-lost-281903/

So the nipple is part #7 in the diagram GM P/N 24422067, also sold by CED

 

Yep, there it is!!!!

Seems like you have to pull the trans again.

 

think i can order the 24422067 pipe and sneak the seal off of it or do i need to put the whole pipe in.

 

From the pics in the link I posted, it looks like you could. It's certainly worth a try!

 

Want to give a heads up on the solution. Ordered a couple new pipes to get the seal I needed. The existing pipe had some marks on it where the seal was so i cleaned that up as much as was possible and put in a new seal and the sleeve. i replaced the entire plastic unit with the seal on the existing pipe. It worked and i no longer have any leak. Big thanks to all who put their thoughts on the board, it saved dropping the engine out again. Thanks

 

That's awesome!!