Is the toilet equipped with a flat plate or a ball type valve.
The plate type can be cleaned and light coat of vasoline to aid the sealing. The same can be done with the ball type , but the ball can be more prone to surface scratches that will drain off the water so a very close look is required, and caution when cleaning the bowl , because even a toilet brush can scratch the seal surface and lead to replacement being required.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.