I have a 1993 Model DU8700XY-1 Quiet Wash Plus. Lately it seems a little to quiet. The pump seems to be running but unless you open the door (or just push the handle release) it doesn't seem to be pushing it through the system. I have noticed when I open the door the water will gurgle 2 or 3 times and when you close the door it is obvious that the water is again circulating. Any Ideas??? Check valve somewhere? anti-cavitation??