Does the top piece come off? Does anyone inspect the insides of these as part of pm? Thanks

Joe, we don't regularly inspect hydroblocks or take them apart unless we have to. Sometimes the screws get seized into the steel bushings that are in the hydroblock body. When you take the top off the rusted bushing may come out of the body instead of the screw coming out of them. In that case you will cause yourself much more trouble, and will probably have to replace the whole hydroblock assembly. And remember that Fresenius H machines have two different hydroblocks with different tops, and seals. The older one has the heater bar threaded into the top, and the newer one has the plate that holds the heater rod in. The change occurred around 1998.