"Lloyd E. Sponenburgh" wrote in message
. net...

My pressure gauge is on the HP line, on the pump side of the control
valve -- so I can see the pressure the pump is delivering, rather than the
working pressure at the cylinder.

The system makes a "screech" when the relief valve opens under full
pressure. That I expect, and don't have a problem with the intermittent
noise. The noise I'm fussing over is continuous while the pump is running
at zero pressure -- just recirculating.

The pump doesn't appear to be cavitating. I've installed a much larger
return filter than necessary, and the intake screen to the pump is clean.
I'm running a low-vis oil comparable to the newer Ford tractor
gearcase/lift
oils (about 5W-20 equivalent). Those oils run quieter than the older
straight-30 I used to use. Also, FWIW, the pump is NOT submerged in oil,
but a free-in-air design mounted on a motor-mount plate.

However, as in my original post... it's not the direct noise from the pump
and motor. I've suppressed that with earthworks and drywall. It's the
"ringing" of the HP line and press frame I'm trying to eliminate.

LLoyd




Try put an acumulator(sp?) on the hp line. That should dampen out the
pressure pulses a bit.
Pat