I've finished resealing my leaky trailer roof...thanks to all the good advice from here :).

Moving on to the windows:  It appears the caulking around the windows has deteriorated and water is coming in between the window framing and the trailer siding (aluminum).  I'm planning on removing the windows and reseating them.  What should I use to reseal them?  I used 3M 5200 on the roof, and it's great stuff, but a bit messy.  What about butyl tape for the windows?

Pam

I am not sure what is best but if I was going to pull the entire window I would use a caulk.

I just washed and cleaned my windows by removing all weather stripping and the glass but not the frame.  And all my leaks went away.  All my weep holes were clogged with pollen and crud.

I would first follow BCB's advice and clean the weep holes and tracks. If that doesn't work, removing the window and recaulking would seal any further leaks. 3M 5200 is an excellent sealant. It is also a structural adhesive. If you were to install the windows with the 5200, it is doubtful that they would again, ever be able to be removed without damaging the frames.

If you like 3M, the 4200 and 101 are good caulking choices.

You might also try a product like Sikaflex's 291, 221, or 201US

I have a Sundowner.  They used a window with a flange & gasket to seal against the outside wall.  The trailer wall was sandwhiched between the frame and a inside trim ring held with screws.  Last, there was a bead of clear caulk around the outside frame.  I think the sealing was done by a foam gasket and the caulk was just for show.  There were areas where the caulk had separated from the trailer wall.

I fixed my leaking windows by removing the frame, replacing the foam seal with one sided adhesive, closed cell foam tape.  It was 3/4 wide and 1/16 thick.  It was flexible enough to curve around the frame corners in a single piece.  The adhesive made it easy to apply to the frame. 

I've never been able to apply caulk without getting it everywhere and on everything.  The tape was very neat.