.
Best to 100% remove the window. If foam seal behind the window lip, simply remove it. Then, apply butyl tape on the inside of window lip. Then, reinstall the window.
To make the window's outer lip look cosmetically good afterwards, simply apply clear ProflexRV (clear @
- Click Here - ) around the window's lip / RV wall (using masking tape to make its edges look smooth).
For a good video, surf:
- Click Here - As shown in above Video, very simple DIY using common home maintenance tools...