If you do some searches, you can see this series of laptop has been plagued with hinge problems. I really feel like it would not have been difficult for them to just design the things without using plastic to mount the fucking hinges. Someone in the assembly line really likes those hinges tight which leads to the plastic breaking where the hinge attaches to the back plate which holds the monitor.

My laptop was under warranty when I called to discuss this with Lenovo. The customer support person was hardly understandable, typical of tech support these days, and pretty much told me to fuck off - this design flaw wasn't covered under the warranty.

Go Lenovo... you used to be awesome. WTF happened?

If you have one of these that is not yet busted and is difficult to open, you'll want to follow this guide. If you have a Y700 that has broken hinge mounts, you can find a new back cover on ebay for about $50.

https://www.ebay.com/itm/New-Lenovo-Ideapad-Y700-15-Y700-15ISK-Lcd-Back-Cover-Lid-AM0ZL000100-3D-Camera/262878595057?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

The fix:

1. There is a little plastic cover on the bottom of the monitor that covers the hinges. Pry it off.
2. From there, there are only 3 small screws holding the monitor in place. Do not attempt to remove the hinge screws yet because a few of them are under the monitor. Remove the three small screws holding the monitor on.
3. You can now just slide the monitor down, out of the back cover. Set it face down on the keyboard.
4. Remove all screws from the hinges. Take the back plate off and set it aside.
5. Use a small socket to loosen the hinge nut. You'l probably notice the hinges are so fucking tight you can't move them by hand when you first start. Loosen them to where you can move them by hand, but such that it still requires some force.
6. Reassemble.