JimFord555
Member
1979 ford 555 lost all hydraulics a few months back and after going through everything time and time again I had a mechanic friend come over and we did some further diagnosing
Found the system pressure was at 340psi and only came up too 540psi when throttled up and lifting up on the rigger.
We knew fluid was bypassing somewhere in the backhoe manifold because with the backhoe bypassed the loader worked fine
Sean from pa replied to a recent post saying to try and disconnect the return to sump line from the backhoe manifold and run the machine. If fluid comes out while all control levers are centred fluid is bypassing internally. We did this and no fluid was flowing (remember to cap the line off that returns to the filter/tank or you will get back flow from the fluid entering the line after the loader manifold)
The only thing I could think to do was to remove all 3 valves and sump pressure test port from the end section of the backhoe manifold (even though I have already had them out individually) to try and grasp what s going on in there and drain some fluid to have a better look. While putting it back together the back pressure valve assembly made a thunk noise so I removed the cap to see it had descended much further into the valve body then I had seen on previous removal/installs. Buttoned it all back together and the machine works perfect !
The back pressure valve assembly was stuck open
Thanks to everyone who helped me through this