I have a goodman (gms80805cnbd) conventional natural gas furnace (installed
2017). i have brown goo/liquid dripping from inside the flue pipe to the outside
of the flue pipe at a connection junction. looking at some other comments, a few
options. One is the flue size, the manufacture's note says 4'' pipe. I have a
4'' to a 5'' to a 6'' line going through the roof. Can the flue pipe start at
4'' and transition to the current 6'' flue metal pipe? Should i look at the
temperature settings, something else or is the flue pipe too large at 6''?