Seriously, did we learn nothing from Futurama & the cautionary tale, "A Head in the Polls"? "[...] nobody can be elected president more than twice." "That's right, no 'body'. But as you can plainly see, I've got a shiny new body." www.youtube.com/watch?v=HvYm68dOQ4k

No pump, I know of, can be overhauled without taking it offline. They move too much which isn't conducive to fine adjustments and create a pressurized system that will lose fluids if opened. That's why the bypass machine was invented because during an overhaul your pump if offline. http://www.nhlbi.nih.gov/health/health-topics/topics/hs/during.html