Any attempt to caulk or seal this area using another method is not likely to have a long term result.
How to seal siding on a mobile home leaking problems.
Vinyl siding institute cited below.
Tree branches and flying debris from a neighbor s yard causes a lot of mobile home roof.
Snow and rain cause the majority of mobile home roof leaks.
The rigid head flashing must be sealed to the exterior sheathing and to the top of the exterior casing fig.
Snow is especially a problem for flat roofs.
Drive a 2 inch nail into the nozzle.
Cut a notch on the ends of the rigid head flashing and bend them down over the sides of the exterior casing.
As we outlined in the second article of this series ceiling water stains and ceiling leaks are the best evidence of an active and or previous roof leak.
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.
Wrap the nail and entire nozzle with aluminum foil or plastic wrap.
Also see peel stick flashing membranes.
The broken j channel is clearly the most likely source of a leak in vinyl siding.