Had problems with my 580C backhoe so rebuilt the valve. Put all new O-rings (88 total) in the valve. When I pressurized the all the A and B ports in the valve (done per the manual) to try to set the secondary relief valves none of the ports would hold pressure. Any ideas on what the problem is ?
The secondary relief valves don't "hold" the pressure they are set at. Using a hand pump - as pressure rises, they release at the pressure they are set at - then when you stop pumping the pressure falls away somewhat, maybe continuing to hold a few hundred PSI - depending on the valve - some may continue to hold a little more than others.