Loader Hydraulic Problem

[Jackfr]

We have a Ford 6640 with a 7411 loader. It doesen't have any lift or curl power unless you deadhead a rear remote. I started this thread back the beginning of May http://www.tractorbynet.com/forums/new-holland-owning-operating/172954-f6640-loader-problem.html It explains what I ve checked so far. We are finally catching up with spring planting chores and have had time to check a few more things. I disconnected the linkage and operated the spool valve directly at the valve to make sure I was getting full travel because of the worn linkage. This made no difference in the loader operation. I checked the signal line pressures from the rear remotes to the proportioning valve and the pressure is 2550 psi but the pressure on the signal line from the spool valve is only around 1600 psi unless you deadhead a remote at the same time as using the loader spool valve then the pressure jumps to the 2550. I checked the check valves as RickB suggested and they appear to be clean and working properly. There is a "hissing" noise when hoisting or curling the bucket coming from the spool valve like you were feathering the valve. So far everything points to the signal from spool valve being the problem as the loader will work fine with plenty of power if you keep a remote deadheaded. That's how we've been using it (hopefully not causing further problems). I have the service manuals for this tractor but don't have any experience in taking apart/rebuilding spool valves. The online NH parts manual lists numerous kits for rebuilding this spool valve, not sure which ones I need. Anyone with suggestions before I jump into this? To replace the linkage and spool valve from NH the parts are close to $3000. Does anyone know where I might buy an after market spool valve joystick combination with a signal line port I have had no luck in finding one or should I try taking this valve out and try rebuilding it.

 

[AKKAMAAN]

You said you have a manual...Right!?

Is there a symbol drawing of the system, that you can scan or shoot a picture with a digital camera, and post it???

That will have info to help out trouble shooting and also to figure out spool configuration for a new spool valve.....

 

[Jackfr]

No there is no symbol manual I can find on some colored flow diagrams that show how oil flows through the tractor. Not the loader as it is an add on. I called my dealer to make sure and he said they didn't put symbol charts in the older tractor manuals and that there was no service manual for the loader only a owners manual. The loader owners manual has a picture of how to plumb it with the four remotes

 

[kennyd]

Did it ever work properly?

According to TractorData.com Ford 6640 tractor information your machine has a Open Center (OC) hydraulic system. I noted in your other post you linked that you wrote this in response to Rick's question about how it was plumbed:

Its t'd into the steel supply line that runs between the proportioning valve and the rear remotes.

With an OC system, you can't have valve's paralleled or Tee'd into the system, all valves MUST be connected in series or the the hydraulic fluid (like electricity) will "take the path of least resistance". The symptoms you describe about having to deadhead the rear remote is the tell tale sign to me that it is plumbed incorrectly. It works when you deadhead the remote because the fluid is forced to the loader valve instead of going through it because it's easier.

Clear as mud

 

[Jackfr]

Yes loader was working fine until sometime in late April. Then it starting going downhill. It still will hoist slowly and lift a minimal amount of weight unless you deadhead a remote. I have never changed the plumbing this is how it was when I bought it approx 4 years ago. The Owners manual (there is no service manual for It) for the 7411 Ford loader says Optional control valve is a closed center (see attached pictures) This tractor has a fixed displacement tandem gear pump system. (Some of the other versions of this tractor have a variable displacement type) It has two basic pumps the main one on the side of the transmission and the auxilary mounted to the front of the engine as shown in picture I posted earlier.

 

[kennyd]

Yes loader was working fine until sometime in late April. Then it starting going downhill. It still will hoist slowly and lift a minimal amount of weight unless you deadhead a remote. I have never changed the plumbing this is how it was when I bought it approx 4 years ago. The Owners manual (there is no service manual for It) for the 7411 Ford loader says Optional control valve is a closed center (see attached pictures) This tractor has a fixed displacement tandem gear pump system. (Some of the other versions of this tractor have a variable displacement type) It has two basic pumps the main one on the side of the transmission and the auxilary mounted to the front of the engine as shown in picture I posted earlier.

Interesting:confused2:

This is contradictory though:

The Owners manual (there is no service manual for It) for the 7411 Ford loader says Optional control valve is a closed center (see attached pictures) This tractor has a fixed displacement tandem gear pump system.

A fixed displacement pump indicates an OC system requiring a OC valve.

 

[Jackfr]

Kenny
I think that is why Ford/NH uses a Priority valve pack on top to the differential. That way they can use the same rear remotes and auxillary valves with either type pump they put on the tractor see attached picture.

Jack

 

[Jackfr]

I really don't know much about hydraulics but I'm starting to learn.

 

[Jackfr]

Learn more than I ever wanted

 

[AKKAMAAN]

Interesting:confused2:

This is contradictory though:


A fixed displacement pump indicates an OC system requiring a OC valve.

It might be one of these closed center/fixed displacement pump systems with a load sensed dump valve (indicated by pos 2, combining valve, on the attached picture)