1971 Ford 3500 hydraulic problem

[todintexas]

Thanks to the help from everyone here my "new to me" tractor has been identified as a 1971 Ford 3500 series with a Vermeer backhoe attachment. I took off the 2 worst cylinders and had them rebuilt, replaced a couple of terrible hoses, tractor runs and all hydraulics work as they should, everything moves. However, no cylinder on the tractor will stay extended. As soon as you let off the pressure, whether it be the loader, backhoe or outriggers the cylinder's collapse back to retracted.

Is this a pump issue since every cylinder on the machine is affected?

 

[Sean in PA]

No, it shouldn't be the pump. When the control valves are centered, the pump is no longer needed to hold the cylinders in position. You should be able to shut off the engine and the cylinders should hold their positions. If they are retracting then either the cylinders are leaking internally past the piston or the control valve is leaking internally, or both.

 

[todintexas]

Thank you for the info, I'll dig in a little deeper. It got better after I flushed the system and put in new oil. But, they still don't hold, not even the newly rebuilt cylinders. I'll look into the control valves, just surprising because it's every cylinder

 

[Texasmark]

You just identified a control valve problem, not a cylinder problem I'd say.

 

[todintexas]

That seems to be the consensus, just seemed strange that it was every valve on the machine at the same time. Tire guy finishing swapping tires onto it this morning, I'll move it over to the shop and start taking them apart.