Not to scar you but, in my old 69 Bronco I had a leak with the drum breaks and it was leaking inside the drum so it took awhile to see fluid come out, and it was a mess. it probably would not hurt to take the tire off and pull the drum and check whats going on the inside.

91 Montero LS "Sandstorm", Auto, Dual Bouncy Seats, 2" Suspension lift, 2" Body Lift, GENII front IFS, 32" MT tires

89 Raider "Trailbreaker", 3.0, Auto, Dual Bouncy Seats