Pump cavitation!

[Isaac Carlson]

I got my splitter converted to electric and put a different pump on it because the old one was worn out.
It cavitates in neutral. As soon as I touch the lever at all it seems to go away. It sounds like rocks running through the pump.
It also takes 1-2 seconds for it to shift to high pressure.
The pump was off of a splitter that rolled over on the road and the guy was parting it out. I went through the pump when I got it and it looked like someone was in there with a chisel. I used the dremel to smooth it out and even reseated the shift ball. I smoothed out the suction inlet and the pressure port to reduce turbulence in the pump. It has a 3/4" inlet and hose, about 12" long and the tank is directly above the pump. The fluid is mostly ATF with some aw46? added to top it off. The pump runs at 3500 rpm. The suction hose is not collapsed and there is no strainer in the tank.
I have some "303" oil I got from a friend if it is worth changing the fluid, but it looked thicker than what is in there.

My oil temp after 15-20 minutes is right at 135*.

I have been working on hydraulics for over 10 years and have never had this problem on anything And I am looking for help to figure out what it is. Could it be the pump is just no good and has internal issues?

 

[blades]

Sounds like it. Should not have been all banged up inside. Mixing oils is not a good thing some do not play well together. Air mixed in oil will give you fits. Pumps are very close tolerance inside.

 

[salecker]

Don't worry about the oil, i mix ATF into my loader hydrolic oil all the time with no issues.
The loader has a site glass that has been sandblasted,straight hydrolic oil is clear and i can't see the level.
Been doing this for over 25 years and no pump issues

 

[Isaac Carlson]

I'm not sure exactly what the problem was, but I fixed it. I was ready to buy a new pump and call it a day, but the pump at the store would not work with my motor. Too many gpm on the high pressure side.

I tore into both of the pumps (the current one and the one it replaced). The oldest one had worn shafts and the seal was shot. It was in pretty rough shape. The newer one still looked good, but the load pin and interstage check ball needed work. I swapped a few parts between the pumps, made a few custom parts, and put it back together. It works! No more cavitation noise and it shifts instantly, shooting right up to the relief pressure of 3,400 psi.