Yes it is fairly common for those to leak. Make sure to replace the shims and all o-rings and seals as well. You need to get a sheet of 600 or 1000 grit emery paper and tape it to a plate of glass to lap the shim mating surface (#18 & #25) to true them up. You can also lap the center section if needed, but do not lap it very much because the thickness is critical to the thickness of the gears. You should also replace the thrust washers (#6) and the thrust bearing (#7) as well. Make sure the check valve (#30) gets put back in the proper location. Good luck.