Ford 1920 - 7108 loader - Control valve

[gdabel]

Can I change the control valve on the loader to a cheaper brand, such as Prince? NH wants $1200 and a double spool Prince, single lever, is around $300. Also, is the control valve open or closed center. I can weld and change the bracket so it will fit, but thought someone might have some ideas.

My original issue was the cylinders leak off, but I have had all four at the hydraulic shop. When I close the block valve on the side of the tractor, the boom will still leak to the ground. When the tractor is running, I cannot pick up a small load, say 300 lbs, without it continously dropping. Any ideas from knowledgable folks would be greatly appreciated. Every NH dealer that I have talked to cannot consensually agree of what I need to replace.

Rear three point will stay up all night and day, and the pump doesn't seem to be the issue. I just need to spend my money wisely.

 

[J_J]

I believe your hyd system is open center, and about 7.8 GPM valve flow.

Here is a 10 GPM joystick replacement valve with float for your loader. PB conversion below.

Surplus Center - 2 SPOOL COMPACT 10 GPM JOYSTICK CONTROL VALVE

Surplus Center - BRAND POWER BEYOND KIT

 

[TraderMark]

The valve that JJ posted is the valve I used when I had to change the one on my 1720 with the 7108 loader.

I wish I could give you some tips and hints on how to make the chage over easier, but it seems that my 1720/7108 were very early models. I had the same control valve as the older 770B loader, not the one that was normally used for the 7108.


Mark

 

[J_J]

gdabel,

If your hyd pump is good, and it can develop up to 2500 psi, and also assume that the cyls are good and leak free. It is almost a sure thing that if you install a valve like the one I posted, the system should work as advertised. That is also assuming that you connect everything up correctly.

You really need a hyd gage anyway to set the relief, and use it to monitor the hyd system.

You are doing essentially what the factory does in accumulating all the parts and then assemble them and provide hyd fluid and test the system.

Keep in mind that new system also fail for whatever reason.

 

[gdabel]

Thanks JJ,

I havehad the tractor at a hydraulic shop, spent $900 on rebuilding two cylinders and the control valve. Nothing changed. The same hydraulic pump, as I understand it, works the three point lift and front loader. I am going to ins tall a hydraulic gauge. Where is the best place for me to connect it? I did close the hydraulic valve on the side of the transmission. I thought this would isolate the system to the control valve and cylinders, but the loader still dropped from six feet to the ground within two hours.

Where would be the best location for me to test the pump output pressure and what pressure should it be?
Thanks for you help.

 

[J_J]

If you have QD's, plug the gage in one of them. That will deadhead the hose when you activate the lever, so only do it momentarily.

A permanent place would be in a tee at the IN port to the FEL valve.

The loader cyl seals could be leaking.

FEL valve could be leaking.

 

[JFS2295]

The pump supplies pressure and volume. While a poor pump may not let the loader lift with it's fully capacity, the pump has nothing to do with allowing a FEL to drop it's bucket with the 4-way in the neutral position. Either there is bypass at the control valve, or there is bypass within a cylinder.

You also haven't mentioned if there is both a problem with lift and curl or just one of those operations.

You could go through the arduous task of checking each cylinder, which would require high pressure caps or plugs of the hose fittings size and a method of attaching the 200-300 lbs on the side of the bucket that you want to test, whether that be another loader or come-a-long.

Lift and block the bucket at a comfortable height, them remove the hoses of the cylinder you are going to test and block the cylinder ports. You could also do the hose if you don't want to loose fluid. Remove the blocking, attach the test weight to that side of the FEL being tested and put the control valve in float position to test the lift cylinders. If the FEL drops, the plugged cylinder is bypassing.

If you are going to test curl, the 4-way valve will have to be moved side to side to relieve the pressure from the non-testing cylinder as you know there is no curl float to the 4-way valve. The tractor does not have to be running during the test, only to raise the bucket into position.

If all tested cylinders are able to hold there own, then you still have a control valve issue most likely.

 

[J_J]

Although you have had the cyl checked and rebuilt, wdchyd, has pointed out to me that if the cyl are not fully pressure tested after the rebuild, there is no guarantee that just because new seals were installed that the cyl is certified good.

It would be nice to see something like this on rebuilt hyd products. Tested to xxxx psi for 10 min, no significant leakage.

It is a good possibility the problem is in the FEL relief valve assembly.

 

[gdabel]

One item that I failed to mention, is that the boom will lift the tractor, but immediately fall when the control valve is in neutral. Also, when I left 700 lbs with the front bucket, it picks it up but i have to keep pressure on the control lever. The front bucket curl did not have an issue; However, before the hydraulic shop repaired the cylinders, the bucket curl would move on its on also.

I am taking off Friday to work on the tractor. I do have quick connects like JJ mentioned, and I will check the pressure there. If that works, I will lift the FEL and disconnect my hyrdaulic lines from the loader. The cylinders should equalize and the FEL stay up; correct. If it does, and the tractor pump checks out, then the only option remaining would be the control valve. Does anyone know if my control valve has one or more relief valves?

I may work on it tomorrow afternoon.

 

[JFS2295]

If you are able to lift the tractor front end and pick up 700 lbs your pump is working fine and you have good pressure. That's not the issue.

The 1710 / 1910 has a diverter valve at the transmission that you are familiar with which retains a 2133 psi relief valve for the entire system. I don't think that's at issue. With a 1710 fitment of the 770B there is an additional 1600psi relief valve installed for the FEL between the diverter valve and control valve so the lighter rear end of the 1710 is not overtaken by the weight in the bucket. That should not be on your tractor.

The control valve does not retain relief valves, but it does have load holding poppet valves.

Disconnecting the quick couplers at the control valve should retain the FEL in a raised position as long as the the couples don't leak and the weight of the FEL alone is enough to compromise the cylinder's seal integrity. It could be one or both cylinders, you can't tell with them hydraulically coupled.

If the curl cylinders are now not doing the same drift or leak down, then at least the shop fixed part of the problem, either within some cylinders or control valve hold poppets. It could be one cylinder, or one poppet.