Pop the wheel off and look behind the drum.
I'd bet the wheel cyl. is leaking or did leak.
Also look at the inside of the rim. Is it wet? Also most likely the wheel cyl. ( or brake cyl. ) same thing.
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1987 4Runner SR5, 4x4, 5speed, 4.7 low, twin stick, Aussie locker
1997 T100 SR5, 4x4, automatic
1997 4Runner SR5, 4x4, automatic, '99 tall coils
1996 4Runner Ltd., 4x4, slight body damage
Look in Classifieds Section for parts
1999 4Runner Highlander, E-locker, 3" OME springs, 1.25" Spidertrax spacers, ARB bumper, 285/75R16 Goodyear MTR