Hi RB and Welcome to The Plumbing Page. at AskMeHelpDesk.com. You're responding to a 4 year old dead thread so I gave you one of your own. Look in then upper left hand corner of the first post form the date in the first post before you post, Thanks,
I unscrewed the cap of the drain overflow
Here's a cutaway of a lavatory. Show me what you unscrewed. Back to you, Tom.