front end loader won't raise unles back bucket is raised also

[goinesp]

I have a 30HP Terraplane tractor . I been having problems with front end loader raising but now I can't get it to up at all unless I work the lift on the back bucket at the same time then it goes up in a hurry. Tractor repair man told me it was probly the Spool valve bad for the loader so I replaced it with no change.

 

[J_J]

Did you install, move hoses on the loader valve?

Is the OUT port going to a tank/return line, and does the PB have a PB adapter installed and routed to the next valve?

 

[goinesp]

Replaced the loader valve with a new one and it still does the same thing, to get the loader to go up you have to work loader stick and the lever for the back lift to raise also, then it goes up in a hurry., the out port goes to tank and it does not have a PB adapter. This is a Dongfeng Tractor. First started having trouble with bucket retracting to pick up dirt. Thought the bucket cylinder were going bad, the started having trouble with the front arms just lifting , but noticed if I played with the back lift at the same time and raced the engine high for more power the loader would go up but now its getting worse, it does not want to go up hardly any now. Where is the relief valve on this thing so I could check it?

 

[J_J]

Most open center loader valves have a relief valve close to the IN port.

The back lift, the 3pt, should have nothing to do with the front valve if things are connected correctly, and in neutral.

If you use all the pump flow for the loader valve, there will be none left for the 3pt, because the cyl fluid is going to tank. Once you release the lever for the loader valve, the fluid starts back flowing to the 3pt.

With all valves in neutral, the pump fluid is flowing through all valve to tank.

If you only use the loader valve, you redirect the fluid to the work ports and the cyl's will operate, and the fluid is flowing into the cyl and out of the cyl to the tank/reservoir.

Now, if you connect things wrong, you may cause back pressure and the pump will have to work against that, and the first valve will not work correctly.

If the hyd is a closed center system, there will probably be a relief valve close to the pump, and you will have a standby pressure at the IN port of each valve.

If you install a 3000 psi hyd gage, you can use it to trouble shoot and monitor the hyd system.

 

[goinesp]

I purchased the exact same valve to replace the old loader valve and took hoses off one at a time to make sure I replaced them back on properly. I bought tractor new and everything was already installed when it was delivered about 8 years ago, it worked fine until about a year ago when I slowly started to have these problems. I do not use it everyday , maybe once a week sometimes letting it sit for a month sometimes. I know what it is doing doesn't make sense but loader will not work with out working both levers now. back lift is starting to get sluggish now and I'm afraid if I don't find out what's going on Il loose my hydraulics. my power steering works of hydraulics but it is still working fine.

 

[J_J]

You say the OUT port goes to tank, but if you have no PB, the OUT is your outlet to pass fluid to the next valve which is the 3pt if it is like a normal tractor.

Can you trace out the flow path through all valves from pump to the 3pt, and then tank?