I've never replaced the roof seals myself. I spoke to Sam Shields about it awhile back. Sam has over twenty years of dealership experience working on Hi-Lo's.
Sam was kind enough to give us the following outline of what is involved in the process. Of course I've added this to our library
In general, you have to remove the roof to replace the roof gasket (seal). It sounds like a big job, but one that is very do-able.
The roof gasket is available from the Hi-Lo factory, here's the number to call, 800-337-6490
My suggestion would be to read though the following outline and then ask any questions that you have. I hope to eventually have a more detailed outline with pictures, or perhaps even a video.
Neal
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Outline for replacing the roof gasket
Removing roof:
You need 6 - 8ft 2x4's
Cut 4 of the 2x4's to fit from ground to bottom of roof.
Lower roof on to the 2x4 blocks.
Remove all screws holding woven wood walls or pocket walls.
Cut wires form lower section to roof at vent pipe and unscrew vent pipe.
Remove all guide rails.
Remove all cap boards
Remove 4 cable bolts from roof.
Fish cable inside camper.
Lower tongue jack to lowest position insert 2x4 across lower wall between lower section and roof.
Raise tongue jack to full up position and insert 2x4 between roof and lower section.
Bring tongue jack back to level
Installing new gasket:
With roof removed cut old gasket off with razor knife.
Staple new gasket in place using molding to hold in place. (molding can be made from 4 x 8 sheet of aluminum cut into strips about 1 1/2" x 8ft)
Lower roof back on lower section by reversing roof removal instructions. Reinstall cable bolts to roof reinstall, guide rails, reattach wiring, sewer pipe, interior wall screws, and cap boards.