Ok, so water is leaking into the ice maker no matter if the ice maker is ON or OFF? and you already replaced the water inlet valve in the back?
That's very odd, then it shouldn't be leaking water in the ice maker, are you 100% absolutely sure that its not the drain trough that's clogged with ice and thus leaking water?
I'd remove the back panel inside the freezer just to make sure.
To Remove the back panel(take all your food and shelves out of your freezer first): The back panel inside your freezer is #11, and #22 is the vent you have to remove as well, The air vent #22 should have 2 clips on both sides of it that you would need to unsnap with a flathead screwdriver first before removing the back panel. Then remove the back panel screws. If you have an ice maker, you'll likely need to unmount that to get more room to remove the back panel.
If the drain trough and drain hole is not clogged with ice, then I'm stumped as well, and you'd need to have Whirlpool come out to see what's going on.
Jake