This is a recent repair here at Ag Enterprise Supply, Inc.  The customer had bought this new last fall and it ran fine but the liquid seal failed towards the end of the season.  While I was inspecting the pump a failure was found in the hydraulic motor.  On Hypro (as well as the Ace brand) hydraulic driven, centrifugal pumps there is a bypass screw on the side of the motor.  It is essentially a needle valve that will allow hydraulic oil to bypass internally.  For pretty much all applications, and on new pumps, I loosen the jam nut and fully seat the bypass screw firmly (not an impact or cheater pipe) then when it is seated tighten the jam nut, also not with superhero force.  When oil bypasses it generates heat as well as losing efficiency at the pump.  What happened was the sealing washer on the bypass screw had failed and was leaking oil, not knowing what it was the customer over tightened the bypass screw which broke off internally and damaged the seat.  When the pump was run after that the broken piece flailed around inside causing major damage to the tank check valve as well as the outlet side of the motor.  Here are some pictures for all the visual learners like me.