i recently purchased a 480f backhoe all hydraulics were slow! it has power to lift a heavy load just very slow i checked oil levels and changed filters, i then disconnected hoses to backhoe (still slow) i than replaced hydraulic pump ( still slow) i checked hydraulic line routing with an infrared therm(the only place additional heat seemed to be generated was in filter housing) i took off housng and inspected seemed ok! there is a bypass valve inside that i am not sure how much pressure is needed to open? first question is should i bypass housing with a hose to see if it helps, second question after the pump on the pressre side there is a flow valve@ it appears it regulates flow to the system and steering, can i disconnect hose to steering and cap it to see if that helps volume of oil to front bucket?
I would pull the spool and spring out and have a look to see if it's sticking. The relief is non adjustable in the flow block but it has a 0-ring on the end that can be replaced. I would not bypass the filter at this time. I am thinking that spool sticking or spring weak or broken could allow the flow back to tank and cause a flow issue. It would not take much to check it.
in the flow valve?
in the filter housing it is a ball and a spring like a backflow preventer (no spool)
Talking about the valve on the frame that diverts the hyd oil and splits off some to the priority steering, it has a spool and spring inside. I would remove the spool and spring and check that it is not stuck (moves free) in the bore and the spring is not broken. Also remove the relief valve in that valve and check the o-ring that seals the lower end of it. Most filters bases have a bypass, it holds some back pressure to insure that oil is being sent thru the filter. If the filter becomes clogged or lube is to thick (cold, cold, weather) the bypass would open sending unfiltered lube thru the system both to the cooler and to the hyd tank. Most are around a 50 psi differential pressure to open a bypass, and I would think you filter light would also be on if it worked.