When I bought my '87 Excella 2 years ago, I took it straight to Jackson Center. They initially found the water leak from dried up caulking around the front corner window. In testing the seal after the repair, they found some water seeping in around the rivets at the seam at the front cap. JC did a complete repair - drilled out the rivets and hand bucked in new ones. After they has sealed all the seams, that night while still at the terraport it rained very hard and I saw a few droplets of water coming out the wall above the bed. The next day we determined that some caulking was needed around the mounting brackets of the 3 solar panels. It has been bone dry ever since (a welcome condition after having owned a '94 LY diesel that leaked every time it rained, notwithstanding all the caulking and Eternabond tape).
1987 Excella 32-foot
1999 Dodge Ram 2500HD Diesel