How to remove a page in its entirety

I'm having a problem with an unwanted page not disappearing, and continuing to be referenced even when replaced with another page. Here's the situation. I have 2 pages with different versions of the same content. Call them page_old and page_new. I want to get rid of page_old first. After that's done, I want to rename page_new to page_old. I'm trying the following, in this order:

1. In Appearance > Menus, remove the menu item for page_old.
2. In my All Pages view, delete page_old, then empty the trash bin.
3. Still in In the All Pages view, edit page_new, change title to page_old, update slug to page_old, save.
4. Here's the problem. The page I'm looking at is not the renamed page_new, it is still the original page_old.

What do I need to do to fix? Another way to ask the question, how do I remove all references to page_old to page_old before renaming page_new?