Loader hydraulic issue

[J_J]

hyndsight,

What is the pressure at each of the work ports?

Can you get relief pressure at each of the work ports?

Plug a gage in work port A, and log in the pressure , Check B, C, and D. They may be A1,B1, - A2, B2

Did you remove the hoses at the cyl, or at the tee to each set of cyl?

Did you check the caps on the bottom of the cyl for rust, etc. If the spool balls and springs are locked due to rust, the spool might not be shifting completely.

 

[hyndsight]

So, still havn't had time to set up a guage yet, but I was digging around a little more today and disconencted the lines at the valve to find the same results, (bucket up, fluid from one port, bucket down, fluid from both). What could cause pressure on both sides of a spool valve? Obviously something is pressurizing the relief side of the circuit, which is partially the reason why I had originally pointed at the valve, but could this be happening in the hydraulic block on the tractor or in the PB circuit?

 

[jinman]

What happens if you push the joystick all the way forward to float? Does all flow stop?

I don't see how anything in the hydraulic block or power beyond could cause this, I think it is internal to the valve.

 

[hyndsight]

Float works fine, as does all function on the boom spool......and yes I agree, I feel anything on the PB/tractor side of the loop would affect both spools/entire valve (if at all), but it seems too much of a coincidence that two valves would have identical defects. Maybe.

 

[Soundguy]

bad pilot / pilot operated check perhaps?

soundguy

 

[hyndsight]

Ummmmm, (forgive my ignorance) are those the two caps in the center of the valve that have spring loaded pressure relief valves under them?

 

[hyndsight]

One more experiment, I connecterd the arm lines to the bucket spool @ the valve. The result was bucket up, in both directions..... after I shut the tactor off and tried to release presure from the lines the arm would only fall a few inches and then stop, like the fluid was not being allowed to return to the tank? Any ideas?

 

[jinman]

So you swapped the lift arms to the bucket dump/curl circuit? Does your joystick have the regenerative position if you move the lever to the far right? If it does, it should allow the arms to drop by connecting both sides of the hydraulic cylinders together through the spool. Other than that, this really has me baffled because something seems to be acting like a checkvalve. Quick connects can do that, but you've swapped lines at the valve and the problem seems to be isolated there and only in one axis.

BTW: Is there any way you could post some photos of your valve and the plumbing?

 

[hyndsight]

Nope, control does not have the regen feature. (And you're not the only one baffled). I'm down to the valve again, but it seems very unlikely that 2 valves would have exactly the same defect. And yes, it does seem like a check valve not allowing fluid back to the tank. Is there some saftey circuit in these valves that could be malfunctioning? Can't do pictures right now, but in all my research this seems as standard a system as there is: pump to block to 2 spool valve with power beyond to run 3ph and standard fel. Simple, right?

 

[jinman]

The 7108 uses a Kayaba control valve. That valve can be regenerative or have a non-regenerative kit added to the valve. It would appear that you have the kit if yours is the non-regen type. I've gone up on messicks.com and copied an illustration of your valve and the installed valve with piping complete. I don't know enough about these valves to tell you what to look for, but maybe somebody can see these and give you an idea. I think if you bought a used valve that there is a better than average chance that it has a similar problem to your original, especially since the symptoms are identical and your original valve started doing this without any change to plumbing. It could be a common problem with older Kayaba control valves, but that is purely a guess and not even a SWAG because I don't even know enough about it to be called 'scientific.'