I kept having leaks. I put a soaker hose on the roof and kept looking. I got them all stopped except in the corners of the windows. There are only two places that seem capable of causing it, and I took it apart to seal them.
I figured it was either these little indentations leaking a little, then it wicked into the area under the window, or....
...in this corner. I figured if I sealed both, it has to stop it.
After removing the crank, I cleaned up the corners and sealed it. Cranks were re-installed, and we'll see.
I really think the leak was in the little holes in the sill. I sealed both the holes and the corners in 2 windows, and just the holes in the third. We'll see.
On to the insulating!
Some of these units were insulated very well. The entire cavities in the walls were filled. Not mine. It must have been built on a Friday afternoon, just before beer-thirty.
So I set to finishing the job about 35 years later. I'm using the cans of "Great Stuff" and foaming it. If course, I have little control of how full I get it, so I'll have to shave a lot off to finish it.