New Hydraulic Weird Problem

[NCMau]

I just installed a PTO pump, replaced all the hoses, QCs and fittings. Prior to this, the loader was operated by the internal hydraulics.
The arms go up smoothly and fast. When they go down, however, they seem to hesitate just like there is a restriction.
When I let them go fast, they seem okay, but when let them go slowly that's when the problem appears. On the down stroke the gauge shows 1000, 15000 and sometime peaking to 2000 psi and the PRV squeals.
Before the new pump installation, the system worked fine, slow but okay.
I don't have the bucket installed because I still lack one hose, but I don't think that would be a problem. The weight of the arm should be enough bring it down. The hydraulic has been cycled may times.
What could be the likely cause of this problem?

 

[J_J]

If you are using QD's, there must be a complete flow path. QD's if loose will block flow path.

If the pressure shows high, that means that you are working under a load.

If you have a large load in the loader, that will show some pressure until the load is on the ground.

If it takes about 2000 psi to raise the load, then the load will apply 2000 psi to the cyl on the way down for a short period.

 

[NCMau]

I like to add that when the tractor is off the arms go down smoothly.

 

[J_J]

The thing is, with good cyl's and good valves, they should stay up. The work ports are supposed to be blocked.

When you push or pull a lever with the engine off, you just provide a path to tank.

 

[bigdeano]

I have a hydraulic valve that does what you're describing. When I move the handle just a little to apply pressure to the load it blocks the flow from the pressure port to the tank port before it opens the cylinder ports, so the pressure relief goes off. It's just made slightly wrong internally. I just have to remember to move the handle far enough and fast enough so it works properly.

I have another valve that lets the loader drop if I don't move the handle far enough. It doesn't have load check valves in it. Not all valves are made perfectly. You may have to just live with it unless you change valves.

 

[J_J]

I have a hydraulic valve that does what you're describing. When I move the handle just a little to apply pressure to the load it blocks the flow from the pressure port to the tank port before it opens the cylinder ports, so the pressure relief goes off. It's just made slightly wrong internally. I just have to remember to move the handle far enough and fast enough so it works properly.

I have another valve that lets the loader drop if I don't move the handle far enough. It doesn't have load check valves in it. Not all valves are made perfectly. You may have to just live with it unless you change valves.

Did your valve do this when new?

 

[bigdeano]

Both valves have always been that way. The valves I've looked inside have the passages in the body just cast. Sand castings can vary a little from one another. Both valves are at least 40 years old.

 

[NCMau]

The thing is, with good cyl's and good valves, they should stay up. The work ports are supposed to be blocked.

When you push or pull a lever with the engine off, you just provide a path to tank.

What I meant is that goes down when I push the valve. Otherwise it stays up for long, long time.

 

[NCMau]

I have a hydraulic valve that does what you're describing. When I move the handle just a little to apply pressure to the load it blocks the flow from the pressure port to the tank port before it opens the cylinder ports, so the pressure relief goes off. It's just made slightly wrong internally. I just have to remember to move the handle far enough and fast enough so it works properly.

I have another valve that lets the loader drop if I don't move the handle far enough. It doesn't have load check valves in it. Not all valves are made perfectly. You may have to just live with it unless you change valves.

bigdeano, I am inclined to believe also that the valve is the culprit. I was hoping it was something simpler. I swapped the QDs and that didn't change anything. I know the cylinders are good and the only thing I changed were the hoses. Something changed in the valve, maybe dirt. Anyway, thanks for the info.