I recently purchased a used splitter with a PTO driven Prince pump made by American log splitter. I am having hydraulic problems. My system seems to be filling with air. With the valve in the neutral position (cylinder not moving in or out) it is constantly blowing air out of the tank vent. When splitting a piece of wood, after contacting the wood it hesitates a bit as though it is building pressure, then the ram suddenly and violently extends out about 3 inches sending the woodflying out off the end of the wedge. I have new fluid and the tank is filled above the return port to minimize air bubbles. I have no leaks, but seems air is getting in somehow. If the ram is partially cycled a few times near the end of the stroke, then returned. The fluid will blow right out the tank vent. Can I be sucking air in a seal in the pump somehow without it leaking fluid? Hope someone can help, this is driving me nuts.