i have 6000,4000,4000hh
all working fine. some have experience auto shutoffs when not place in a well vent places. the pumps have a built-in themo sensor to prevent meltdowns.
crankin noise when bubbles r trapped in the pump like when just started. sometimes, it clears on its own, but sometimes it needs to be shut off a few secs,then back on.
I have had the 4000HH as a return and running a skimmer and loved it. I also have a 3000 feeding my chiller and 2 phosban reactors and it works flawlessly.
i have the 4000 and it sucks...ill never buy another quite one...and its not quite iether....when you take it out of the water to clean it ..it can be a pain to get it flowing again and you gotta pop off the lid and i broke the shaft 3 times doing that because water creates that tight seal...i would not recommend this pump...id rather have a temp noisey mag...