OK! Thank you Txarvee for the PDF ,I learned a lot about the sewer system.
So the fix was easy. Went on the roof, removed the vent covers and found two of the three sewer vent pipes were to long and were right up against the cap, so no air flow. With my Demmel tool, removed about 1/4 " of pipe re-installed the caps, caulked,and it seems to be working.
So thanks again.
John & Karyn
2012 Eagle Super Lite 31.5 RSLT,
W/ Reece Sidewinder hitch
2008 Chevy 2500HD crew cab,