Thanks KBPsen
Many years ago I experienced a complete loss of System A Hydraulics oil contents in a 737-200 just after lift off when the landing gear hydraulic down line burst.
After landing I recall the engineer had to change both engine driven hydraulic pumps as part of the rectification process. This apparently was because loss of hydraulic oil to the System A engine driven pumps caused damage to something to do with a case drain.. Sorry if I am a bit vague on the terminology but I do remember the poor old engineer worked through the night in the open with winds and pissing rain to change the pumps.