Gordon --

I think leaks often occur because rust has begun under the rubber gasket. The rainwater "wicks", by capillary action, through the pores of the rust. It may be worth the time 'n trouble to remove the window -- and clean, inspect, repair, prime, paint, and/or seal -- as needed.

The rear side windows (at least in the wagons) can be removed from inside out by carefully (and slowly) prying the inner edge of the rubber gasket up 'n over the metal lip -- and working your way around 1/4" at a time.

The wagon windows must come out from the bottom, leaving the top engaged with the lip. Sorta like a casement window. If you try to remove the top first, the rain gutter blocks the window.

You need a partner to pull out 'n catch the window -- otherwise the concrete floor catches the window (BTDT).

Reinstalling the window is easy:

• Wrap mechanic's wire or heavy cord (not rope) wire completely around the groove in the gasket, both ends ending and overlapping in the top groove. Don't tangle or cross the ends.
  
  
• Apply soapy water to both the groove AND metal lip, all around.
  
  
• Have your partner insert one side of the groove (top edge) over the metal lip from the outside. That is, install it over the lip.
  
  
• Partner holds window up and pushes in (yeah, I know -- soapy, slippery).
  
  
• You, inside car, pull one end of cord. This "zips" the edge of the rubber gasket over metal lip. Be prepared with a small tool to help pry the rubber gasket over the lip, if needed.
  
  
• Be alert to getting the bottom edge to properly "zip" over the metal lip -- since the window's weight tend to pull it down, that rubber edge will be the most stubborn. Your partner must lift 'n pry upwards.
  
  
• The decorative metal trim on the outside of the rubber gasket can stay installed in the rubber. Try not to bend, kink, or ding it. As I recall, reinstalling that trim into the gasket is a PITA.