hydraulic system

[David in TN]

The bucket on my tractor would not stay rotated up. The loader its self would stay up, but the bucket would rotate down into the dump position. So I removed the lower lines on the bucket cylinders and put plugs in the cyls and lifted the loader and it stayed up. So I replaced the valve body, figuring the spool valve was leaking. Well, I cranked it up last night and it still does it. One thing I know I need to fix is the valvebody (you can see it at the link below) is open center and I am going to order a kit that will make it closed center. But it don't seem to me that would make a difference. I probably didn't run it long enough to get all of the air out of the system yet and I'll do that this am, but I'm not so sure that's it. To me it acts a lot like it did before the new valve body, except it operates a lot faster and smoother.
=&data[catalog]=1&data[itemcode]=7111598]Valvebody

 

[Anonymous-0]

Have you already put new O-rings in the cylinders. If your goin to fix the valve body might as well make sure oil isnt by passing in the cylinder too and be done with it.

 

[lfn]

You Say "I removed the lower lines on the bucket cylinders and put plugs in the cyls and lifted the loader and it stayed up". would still not be a test as one good cyl and one bad cyl would still hold the bucket up because you closed off both and the good cyl would hold it up.
The best way to check piston seals is to apply pressure to the rod end and see if oil flows to the other port internally, or it can be done with pressure applied to the butt end. just make sure which ever you choose that the cyl is in the open or closed position before appling pressure or some one could get a oil bath. As much as yours leaks down you likely could check the piston seals with air pressure
Also you don't mention as to the type pump your tractor has. Both pump and valve MUST be compatable

 

[David in TN]

Yea, I thought about one good cyl would hold it up. I will check each one. May rebuild both. But It don't make sense that it would stay up with plugs in the cyls, but not with the lines on with bran new spool valve. I did notice when I removed the plugs pressure build up was a lot more in one cyl than the other. JD Manual says the system is a closed system, would it hurt to run the open valve body for a few days until the plug kit comes to make it closed center?

 

[buickanddeere]

Not a good idea to try that "Farmer fix". The tractors front pump will be pumping 100% capacity all the time. The front pump will cavitate as the trans pump can not keep up. Particularly if the return line from the loader isn't routed back to the trans filter were it belongs.
The trans/hydraulic oil is going to get awful hot too.
System pressure will be low on the trans pump to the brakes, pto & high/low shift.
Power Steering will be non existent unless you are lifting the loader at near max capacity.

 

[430WLPG]

the easiest way to find the bad one without a oil bathis, if you have acess to one of those laser thermometers, retract the rod to the butt end and hold it there on pressure for probably 2 minutes then take temp reading from the same area on each cylinder and the bad one will have a higher temp probably just 8-10 degrees from the bypassing fluid