[George1]

Thanks cTesla. This is narrowing the problem. Appears that this is not a mechanical issue. If one of the tubes is gummed up, does the screeching noise come from gas passing through a restricted opening. So that whacking the top of the filter, some of the gunk shifts. Sounds like that is what you are saying. Don't need to get a huge discussion going here, I am just trying to understand it a bit. Could the noise come from the desiccant being plugged up inside the filter?