The pump is mounted on the bottom of the hydraulic unit. When you remove the pump check the o-rings that mount the front pump flange to the hydraulic base plate. A damaged o-ring can cause loss of fluid to the rear end.
To disassemble the pump, clamp the front flange in a vice protected with some cardboard to prevent damage to the o-ring surface. Drive the dowel pins part way out of the pump and remove the wires on the bolts. Not all pumps are wired. Remove the rear end plate to just inspect the pump. Drive the dowels all the way out and remove the bolts and disassemble.
Look at the centerplate for cracks. These can break from water in the system and freezing. The plate will also break from excess pressure from the relief valve set too high. 1200 PSI should be the maximum to run the system. The pressure can also run too high if the relief valve seat is loose in the base plate. Pressure will push it and the relief valve plunger out toward the spring and not relief oil to the reservoir. The excess pressure can damage the pump. Be sure to check the relief valve seat.
The gears should not have material on the tips of the gears and the sides. The end plates should be smooth and not have wear marks that catch your fingernail when you drag it across the plate. End plates can be reground by a machine shop. The shafts should smooth on the bearing and seal surfaces. Any excessive roughness will cause premature bearing failure. If the shafts have worn beyond allowable specs, the bearings will not hold the shafts in the correct position and the pump will likely fail prematurely. The gears should have no additional material on the gear teeth or on the sides of the gears.
The seals and bearings need to be removed if the end plates need to be ground. The Oliver manual instructs one to remove the bearings with a pilot bearing puller. The bearing cage can be cut out with a torch or a very small hand grinder after the needles are removed. Be careful not to cut in to the end plates.
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