shaft seal 40 is positioned between second expansion chamber 44 and scavenger chamber 24 a second passageway 42 is located proximate to said second shaft seal 40 communicates with scavenger chamber 24 and second expansion chamber 44 second elastomeric bladder 46 is present in second expansion chamber 44 as can be seen in fig2 a second elastomeric bladder 46 defines a second overflow motor fluid encasing volume 48 and a well fluid encasing volume 50 third shaft seal 51 is located between pump 22 and second expansion chamber 44 scavenger material 52 is located in scavenger chamber 24 in operation shaft 18 is driven by motor 20 and drives pump 22 motor 20 generates heat during operation this heat warms the motor fluid as the motor fluid becomes hot the motor fluid expands the path taken by the expanded motor fluid is indicated by arrows in fig2 a c initially the motor fluid migrates into first expansion chamber 28 where it fills a first elastomeric bladder 30 when elastomeric bladder 30 becomes full the motor fluid migrates through a first check valve 36 out of the motor fluid encasing volume 32 and into the overflow motor fluid encasing volume 34 the.