Folded Seams?
 

I bought a used 1992 26 ft. Hi-Lo last year after carefully checking the ceiling for water damage. I should have been checking the WALLS! It is a nice Hi-Lo so I don't mind working on it but it has the aluminum roof that someone had smeared every joint (every 3 ft. or so) with silicone so I started cleaning seams and end cap joints and got to thinking over winter if each of the aluminum joints (which appear to be some sort of crimp joint ) are supposed to be caulked. Does anybody know? I have wall water damage in two or three places two next to windows except for the bathroom wall behind the mirror (door side) which i suspect is blackwater tank vent. but no discoloring on ceiling but wall is soaked. Window caulking doesn't look great could it be wicking from a window leak?

The aluminum roof crimped joints do not come from the factory caulked, but caulking them should not hurt anything, I caulked our 95 and I caulked our 2209 as soon as we got it. Have you checked the caulk around the black & gray water vent, also check the caulk around the air vents. The molding at the top along the edge is also a place for a leak to occur especially in an old trailer, the original caulking which is under the molding, drys out and over the road flexing causes a leak especially where the screws go in. The insulation in the roof or paneling could also run a water leak to the side wall.

Side wall water leak
 

Take out your windows and this will show how much water dammage you have. Start by going on the inside removing the ring and screws. This is a two man job. Gently pry on the outside with a putty knife. Reapply the window with butyl tape/sold at rv dealers. If you have a delaminated rotted wall then you are talking a rebuild before you reinstall the window. Back off your screws to awninga a caulk screw and hole. Out side lights need to be sealed up with calk. Misery loves company. We went from a popup to the HiLo and didn,t know anything about delamination. Could have beenpresent when we bought it and has gotten worse. My husband just wants to use the trailer as is for fear of messing it up while rebuilding the walls. Window take out/one person onthe inside and one on the outside when removing. Window is awkward to remove. After reinstall keep checking all the screws for looseness with travel. Still learning much from this forum. Next summer I want my semiretired husband/sheet metal fabricator to do a major fix on the HiLo. He says he is afraid to maKE THINGS WORSE. i BET i WIN THE ARGUMENT!!

Thank you both, I think starting by removing a window is a great idea, also the side that has most issue (door side) has the sloppy remnants of a awning removal. Has anybody seen a 45 degree crack above the door in the top half? Up and down works great as does the door but I guess I probably know what it is.

HiLo repairs
 

Could you take a picture of the crack and post it for us to see? We could help you better.

I will try to do that this weekend, I see around the vents ac antenna etc. it looks like something for roofs was poured on, not messy (it has cracks) can anyone tell me what that might be? Thanks