The rigid head flashing must be sealed to the exterior sheathing and to the top of the exterior casing fig.
How to seal siding on a mobile home leaking problems.
Cut a notch on the ends of the rigid head flashing and bend them down over the sides of the exterior casing.
Completely replacing or installing vinyl siding directly over aluminum or wooden siding on a single wide mobile home may cost approximately 1 000 2 500 for labor and material.
I would recommend removing the siding around the window and replacing the j channel.
While flat roofs aren t completely flat they don t have much of a pitch and that allows the snow to just sit on the roof and melt slowly.
Snow and rain cause the majority of mobile home roof leaks.
Also see peel stick flashing membranes.
Wrap the nail and entire nozzle with aluminum foil or plastic wrap.
Drive a 2 inch nail into the nozzle.
The broken j channel is clearly the most likely source of a leak in vinyl siding.
Any attempt to caulk or seal this area using another method is not likely to have a long term result.
If you still have a half full cartridge or you just need to take a break between stages of caulking then there are two ways you can keep your sealant soft and ready for the next use.
Vinyl siding institute cited below.