the screen hinge is loose on my 27 inch iMac and was looking for a fix. Saw one utube video on removing the display but wanted to know a way to tighten up the display using the 8 torx screws that are suppose to be behind the display mount that holds the screen to the mount.
There is a part broken inside the computer, the only effective repair is to get it replaced. Take it to an Apple Store (not a reseller) and they will likely do it at no charge.