I realize that this forum is mostly about appliance choice, but in the past I have seen that there a couple of people who were familiar with appliance repair. I am hoping they could point me in the right direction. I am generally handy and well equipped.

I have a poorly cleaning ~6 year old Maytag Quiet Series 300 Dishwasher. The first problem was that while dishes appeared clean, deep cups retained little dots of crud that could be easily removed by hand afterwards (not stuck on). That suggested a failure of the backwash filter that this unit claims to have. I have removed the large disk fine filter below the bottom sprayer and it has been completely clean. More recently, some dishes failed to clean at all and then I had to remove everything down to and including the little ~3 inch diameter, ~1/2 inch thick disk impeller because of a small piece of trapped broken glass that made a big racket. I have also found that my bottom spray arm has become somewhat worn and the threaded plastic cap that holds it on was really damaged so it didn't hold that sprayer exactly horizontal. I am working on a jury rig fix for this. However this spray arm does rotate during operation.

However, my larger problem appears to be that neither the top or middle spray arms appear to rotate. They almost always remain in the same location after 30 seconds of operation. Water does get up to these sprayers. When I open the door, water is still pouring down and I can see water still gently rising from the middle spray arm. My assumption is that the pumping action is not sufficient, but I am wondering if I don't understand the system completely. Is the 3 inch disk impeller the only pump, or is there something else to check out? This impeller seems kind of small for the job but I can't imagine where else water could be picked up from. The impeller is not damaged and it fits well on its shaft so I don't think it can slip.

Upper arm water is delivered from a manifold surrounding the impeller that rises at the center of the back wall and curves to the center of the top of the washer to a small spray arm. The middle arm picks water up from a tube that slides into the manifold thru a flex rubber flapper (there are actually two flaps; one is unused and remains mostly sealed). I worry about this connection because some water can easily slip by this fitting. However, there is an additional open hole in this manifold where a far greater water loss could be. This oblong ~1/3 inch by ~1.5 inch hole which points to the side of the washer does appear to have the capability to be connected to some non-existant (in parts breakdown) fitting. I have mostly closed this hole off with a piece of plastic hose hoping to raise the water pressure in the manifold.

I have seen references on line to some seal that is supposed to improve things, but I don't see how this would help and it appeared that the replacement would take a repairman a significant time and expense. Does anyone have any experience with my issues?