Joystick issues. Need a hydraulics Guru!

[Kernopelli]

I recently put my loader back on ( I've used this same FEL and valve on the tractor about 7 yrs) and noticed a problem right away. Initially, the FEL would lift, lower curl but not dump. I figured it was a QD so I reset it but still had the same problem. After doing this several times, I eventually took all the hoses off the valve and cycled each valve function so I could see the actual hydraulic flow from each port. When I curled the bucket, fluid came out of the correct valve port but when I dumped the bucket, fluid came out of both curl and dump ports. I took that spool apart and could see ( cant "see" much since it is a solid cast valve body) the spool rod looked fine ( clean, smooth and no nicks etc) , it seemed to be centering in the valve body correctly and I wasn't able to flush or blow any debris out of it.

I reassembled the valve and now the curl/dump spool works but the other spool is exhibiting similar issues. The lift works fine but the lower doesn't ( I am assuming I now have fluid coming out of lift and lower valve ports at the same time when I try to lower the FEL). Also, the 3pth now doesn't have flow unless I curl the bucket at the same time I lift the 3pth. I haven't yet taken the lift/lower spool out but I am baffled.

This is a Ford NH Zextel valve. Anyone have any advice? Since there is no way to access the complete internals of the one piece cast valve body, I am assuming the only Orings/seals are the ones at each end of the spool rods and close tolerances between the spool and valve body are what "seals" fluid flow and prevents it from "leaking" past the spool rod and into multiple internal fluid paths/valve circuits...is this correct? The reason I assume there isn't internal orings is that I can see no way to install them since the Valve body is one solid cast piece. What can would cause this and is it repairable?

 

[J_J]

Have you removed the load check valves .

When they fail, you see weird problems. .

There should be a spring on a poppet, keeping fluid from returning to the input port. Could be worn, broken, debris jamming the valve open.

Check the relief valve for debris.

 

[Kernopelli]

Thanks JJ. I only saw one check valve and I did take it out and inspect it. Both the valve seat and poppet looked good and the spring "appeared" fine (not broken, length looked right and seemed to provide good compressive force against he poppet). I assume if the check valve is faulty, it WOULD allow flow in two directions (correct??) If so, does it make sense this would cause fluid flow to both ports on that spool? Also, did I simply not notice there were 2 LCV's ( one for each spool) or is it common ( or possible) that there is only one?

I haven't checked the relief ( it is a separate Prince adjustable PRV) installed in the pressure line before the valve. This Zextel valve isn't equipped with an internal relief. I have had other relief valves stuck partially open due to debris before but since this isn't an internal valve, I didn't think it could be the culprit. I haven't put a gauge on anything yet but it appears I am getting full pressure to the valve itself and it is relieving correctly when the valve sends fluid flow to cylinder extend and retract ports simultaneously.

I am going to remove the valve again tomorrow and inspect the lift spool ( I only checked the curl/dump spool the first time since originally the lift/lower spool was the correctly working spool) . I'll recheck the load check too. Any thing else come to mind that I can do?

 

[J_J]

There should be a load check for each spool.

If the spools are good and clear, fluid should only flow through one set of orifices for each work port.

If all valves are in neutral, you should not have any or very low pressure in the flow path.

You say that you have to activate the 3pt to make the loader valve work, that tells me that back pressure is messing with the loader spools.

Find the 3pt neutral and then try the loader valve again.

Take some pressure readings and tell me what you observe.

 

[Kernopelli]

There should be a load check for each spool.

OK, I'll check for a second LCV tomorrow.


You say that you have to activate the 3pt to make the loader valve work, that tells me that back pressure is messing with the loader spools. .

Actually, it's just opposite......the 3pt wont lift unless you cycle the joystick valve's curl function.

 

[J_J]

Did you double check your hoses for correct ports.

 

[Kernopelli]

I did check the hose positions....doesn't mean I didn't get it wrong though . The correctly working loader functions did respond with their respective joystick movements though so that makes me think I must have had the connections right.

I just got back in from disassembling the valve. I took both spools, both check valves out and removed every part/piece that comes off/out of the valve body. Everything looked good. I flushed it, reassembled the valves and spools then blew low pressure compressed air through the pressure port and cycled the spools to make sure flow path was right. I found nothing wrong with anything. I don't have time to hook the valve back up today but hopefully tomorrow afternoon or Monday A.M. I can see what happens.....I'm not optimistic since I didn't find anything unusual but who knows? Strange things happen.

If this doesn't work, guess I'll just put another valve on it. I have a new 3 spool I bought for a song on Ebay. It's not a single lever joystick but hey, maybe this is my opportunity to make some rear remotes or a grapple......make lemonade from life's lemons as the old saying goes.

 

[Kernopelli]

Well, I put the valve back on, hooked everything up and it appears to be working right now. Never did find any debris, leaking seals, damaged spools, improperly seating check valves or anything else unusual, I am thankful that its working and especially thankful for the help J.J.!! It REALLY bothers me to have a problem that "fixes itself"....you're always glad it's working but you don't know exactly what caused the problem or what fixed it. Had a pneumatic problem at work yesterday. Same thing, wasn't even close to working correctly and after much work done by 3 fairly intelligent/ capable people, we found nothing....yet after reassembly, it is functioning correctly again. You always suspect what action was the fix but in the end, you don't have a definitive answer. I think this issue was a Load check valve but I certainly can't prove it. GLAD to be back in business though ( at least for the time being)!!

Thanks again JJ!!!!!!!!!!