Expansion tank cap stuck!

[Rouvld]

So today I noticed that my coolant light was on so before I set of I thought I'd top it off. But when I went to unscrew the cap it actually separated, the top of the cap came off I'm my hand and the threaded part is still stuck inside of the tank opening. Any one have any idea how to remover it? I've tried to rescuers the tip of the cap back on then tried to unscrew it again but it didn't work. My car is an 89 by the way.

[Kershaw]

Drill it, cut it, break it, the smaller of pieces it is in, the easier it'll be to remove.

[Click]

Happened to me once. For some reason the insert and outer cap are designed to just snap together. I was able to pull/wiggle mine out. I snapped the parts back together and continued to use it for quite a while before I bought a new cap from blunt