The actual source of water leaking in can be very difficult to determine sometimes because water will travel from the source to the actual point where you see it appear. I've spent many hours trying to eliminate
leaks in our
Uhaul. Still not done but I'm making progress. Greg, do you have the old style square corner
windows, or the newer round corner type. Are there any drain holes that could be plugged. We have a new
Scamp jalousie window in the side of our
Uhaul, and after I removed the foam tape that
Scamp sent with the window and reinstalled it with butyl tape there was no more leak. You may have to use a hose to run water on the trailer, start low, work your way up until the leak appears. I've even had
leaks through tiny flaws or chips in the
fiberglass. Just this past weekend I discovered that what I thought was a leak around the window turned out to be a flaw in the
fiberglass seam.