I would suggest hiring a private investigator/people locator service first. If you find him, send him a quitclaim deed to get his name off. If you can't find him or he doesn't return the deed, then file a quiet title action and ask the court to extinguish his interest based on the costs you have paid over the last several years. You will have to serve him by publication if he cannot be found.
The general advice above does not constitute an attorney-client relationship: you haven't hired me or given me confidential information by posting on this public forum, and my answer on this public forum does not constitute attorney-client advice.