This is the reason I asked whether your rear window shocks are strong. Mine were very weak and wouldn't even hold up the window. Likewise, I'm sure they weren't strong on the collapse to the down position either. I replaced them. They are cheap and easy to replace. It takes a lot of force to lift my rear window now, because it is seated so firmly. If you put slight pressure on the window and it stops leaking, your rear window shocks may just be worn out and not holding the window very well. If you push slightly on the window and it stops the leaking, as you said, then the problem seems to be at the bottom, or sides, on the window, where the shocks would hold it. You really can't press the top of the window to stop it leaking because the hinges don't move. So, you must be pressing on the bottom or middle where the bottom pivets on the shocks. The shocks may just be worn out and not holding the seal on the sides or bottom very well. Mine collapse firm and strong now, once I replaced them, creating a good seal. Just a thought and suggestion. If your shocks hold the window up firmly and strong, then the issue may not be the shocks. If they don't, then I believe the issue is the shocks.