I have a steel framed bicycle with internal routing of the rear brake cable. It goes into the top tube behind the head tube junction, then emerges near the seat post junction. It has the little eyelets in the TT where it goes in/emerges that are part of the frame. (sorry don't know the proper word for them.)

The brake cable housing runs into the TT and continues for the entire length, coming out the rear eyelet and continuing down to the brake.

The problem is that the housing has split where it enters/emerges and the inner wire coiling has seized to the frame. No amount of pulling/pushing, WD-40 soaking, etc. has dislodged the cable or corrosion.

I'm wondering what is the best method of getting the housing un-stuck?

I thought about carefully drilling it out, after removing the cable, but I need to free up both ends. If I drill at both sides, it seems like the piece of housing inside the TT would then be pushed in and drop inside the TT. This doesn't seem like a good thing, but maybe I could remove the fork or seat post and fish the piece out?

I'm hoping someone else has run into a similar (frustrating!) issue and can provide some expert advice.

And, of course, once this is out I'll have to figure out how to thread in the new housing without anything inside to guide it, but that seems much easier than this removal challenge. (I do think folks have used vacuums to get the new housing in. Or, if I do end up pulling the post/fork maybe I could just guide it in that way. I'm not positive though, having not pulled the fork/post yet if I have clear access to the TT)

Thanks!