Our Bosch dishwasher is about 6 years old. Over the past few weeks, it has started making a horrible cavitating noise at the beginning of each circulation portion of the cycle. Initially, we thought there might be some kind of scale buildup and so we just ran a couple of cycles with dishwasher cleaner. That made no difference, and so we started examining the situation more thoroughly. We noticed that even though the dishes were getting clean, the water levels during the cycle (particularly during the noisy parts) were lower than we expected to see. We don't have a great baseline for what the water levels were historically, but we expected it to be above the sump screen. Generally, when we open the dishwasher during the noise, we find the water level to be at or lower than the height of the sump screen. The noise does go away if we open the dishwasher when the noise starts and add a few cups of water. This is how we've continued to clean our dishes over the last few weeks. The noise very reliably disappears the moment we add more water. Based on this, we replaced the water inlet valve thinking it must not be opening enough and causing the machine to underfill. The new water valve did not resolve the issue. Next, we pulled the dishwasher out of the cabinet to inspect the water manifold and tubing for debris. They are beautifully clear. We do have a water softener, but even so, it still surprises me just how clean the tubing is. We reconnected the water to run the dishwasher and watch the water manifold at the same time. Water definitely enters the machine, but just doesn't fill it to the level required to avoid the growling sound before the circulation pump kicks on. It continues to fill for a minute or two while the circulation pump gets going, and the majority of the time the noise goes away by the time the filling ends. Even that end level is somewhat variable though, which surprised us because we expected it to consistently fill to a point that would almost - but not quite - trigger the float. We've played with the hose to make sure there are no kinks. The only other thing that I can even think to do, but have little hope for and don't really know how good of an idea it really is, is to vacuum out the sump and each port entering/exiting the sump just in case some chunk of food is managing to stay bizarrely stuck through weeks of troubleshooting & running the machine.
My question boils down to: what next? What is the normal fill level for a Bosch dishwasher? Is this fill level normally variable, and if so, by how much? What other components would impact the fill level and could potentially cause underfilling? Or should we just move over to focus on the (much more expensive) circulation pump and ignore the variable water level?
If the noise is like a jumpy or chattering noise then you will want to check the water pressure coming into the unit. If the water pressure is too low it will cause the unit to have the chattering noise.
Answered by AppliancePartsPros.com | Tuesday, October 08, 2013