Quick Attach Hydraulic Problem

[kennyd]

The only way the cylinders can move like that is if the valve lets them. I still say the valve is damaged. Maybe it's just the load check that are damaged, but I don't think you can replace just those unless this is an aftermarket valve body.

If both piston seals in the cylinders where blown, then oil would be leaking out of the vents since these are SA cylinders.

 

[RedNeckRacin]

I appreicate the help fellas but I'm telling you the valve is not bypassing fluid. If it was the plow would stay exactly or close to where it was moved to. The plow springs back to the exact same position that it started in before I contacted the object. That tells me that the fluid is being pushed into the hydraulic line and is forcing it to expand (scary stuff). When the pressure from the plow is taken away from the cylinder, its going back to the cylinder that it came from to put the plow back to where it started at. Maybe I need to replace the hoses with higher rated lines so that they aren't as effected by the cylinder back pressure?


I had not thought about pilot check valves. I was just thinking check valve as in one direction flow. :confused2:

 

[kennyd]

Ok, good luck. But there is no way the hoses are expanding that much, unless you used garden hose to plumb your grapple.

 

[RedNeckRacin]

Nope, I used hydraulic hose from the local equipment shop. Also used brand new 1/4" line for the connection to the snow plow up to the QD on the hydraulic line.

How else do you explain the plow returning back to the original position?

 

[kennyd]

How else do you explain the plow returning back to the original position?

Simple. Pressure on the inlet side (towards the pump) of the valve overcomes pressure at the work ports AFTER the resistance is let off of the blade. When your against something with the blade the pressure is higher on the work port side and the fluid leaks past the spool and the fluid goes back to the tank. My WAG is there is a crack in the internal casting or passageway in the valve.

Of course this is all just my theory, but there aren't many explanations of where the fluid might be going otherwise since it's not running onto the ground.

 

[RedNeckRacin]

If there was fluid bypassing anywhere in the valve and going to the tank, the plow would not return back to the original starting position.

 

[TimBuck2]

Extended cylinder compresses with load then springs back when load is relieved?

sounds like you have air in you system. Maybe a pocket caught in one or both cylinders.

 

[RedNeckRacin]

Yup, that's pretty much it. Just SA twin cylinders.

That's about the only thing that makes much sense to me at this point is trapped air. I don't know that I have a real good way of trying to bleed it out though. The hoses from the rear outlet are over 12' long plus the 4 footer's from the SA cylinders back to the quick couplers. I think I assumed that the air would naturally be cycled out of the system but maybe I haven't been diligent enough about chasing all of that out yet.