Loader Loader won’t go up and down

[JeffWebb]

I have a 2019 B2601 with LA434 loader
A couple weeks ago, it slowed way down on about my 20th load of sand moving. It then stopped going up/down at all within the next 2 loads.
I’ve replaced the load control valve (very expensive), the QD’s for the hydraulics to/from the loader, rebuilt both cylinders, changed the filters and fluid (not necessarily in that order).
I put a pressure gauge on both sides of the up/down cylinders (one side at a time) and pressure is ~2000 psi (using a 5k gauge), it appears it is getting full pressure to both sides of the cylinders at the same time.
I’m dumbfounded, can’t think of anything else it could be.
Any help would be appreciated!

All other functions work fine including the bucket.

Thanks
Jeff

 

[JWR]

It sounded like the auxiliary hyd pump would have been the first place to look. Especially before doing all the expensive things you did. Are other things driven by the hyd pump working well ? Real puzzle is having good measured pressure at the loader frame cylinders and yet it won't go up /down !!?? YOU DID SAY that other things work fine like the bucket... by that you mean drop and curl of the bucket I am sure. And I am sure you realize unload may well appear normal and really be dropping due to gravity rather than hydraulics.

So... if the bucket curls OK AND you have pressure at the two cylinders and yet the loader frame will not rise on command... that would dumbfound all of us. Maybe clarify a little what you mean by "full pressure to both sides of the cylinders at the same time." I assume you meant full pressure on ONE side of each of the two cylinders? Possibly the pressure is OK statically but when in use the pressure dies off over time? Maybe still a pump issue?

If all this discussion clears the air without a solution, I'd be thinking some problem with the loader valve. Those buggers can be tricky. I had a bad one on my MF DL250 loader and went through TWO bad "new" ones coming straight out of AGCO parts depots. All under warrantee. Baffled the dealer and myself until I called the loader valve manufacturer who admitted "yeah, we let a few bad ones out of the house" and he mailed me a kit to use on the spools to adjust the length of the machined spools relative to the ports. Installed the kit myself and cured the problem. AGCO had an unknown number of bad ones in their "new parts" inventory and I found 2 on dealer lots as well.

All that said, it would be surprising if the LA434 loader valve had those kinds of issues. The smaller loader valves like yours tend to be simpler and WAY more reliable with fewer idiosyncrasies than the needlessly complex more expensive ones.

 

[oldnslo]

If pressure is on both sides of the cylinders while attempting to raise something is restricting or blocking flow from exiting the rod end. Most common culprit is the quick disconnects.

Can you put loader in float? If yes does pressure drop on both cylinder lines?

Have you tried connecting lift lower lines to curl dump to see if it now operates?

 

[JWR]

If pressure is on both sides of the cylinders while attempting to raise something is restricting or blocking flow from exiting the rod end. Most common culprit is the quick disconnects.

Can you put loader in float? If yes does pressure drop on both cylinder lines?

Have you tried connecting lift lower lines to curl dump to see if it now operates?

Yeah, that is what I was getting at by asking him to clarify what he meant by "full pressure to both sides of the cylinders at the same time."

 

[JeffWebb]

Thanks for all the quick feedback! Much appreciated!
The data of having full pressure on both sides of the cylinders in discussion with Messicks tractor parts technician led to checking the QD that I have to disconnect and connect to backhoe when used, this QD ended up being the issue. I had removed the backhoe a week before this issue. I was 20 loads of sand moving when this issue arose. So I suspect FME when I reconnected the hose from the backhoe to the tractor which led to failure/blockage of the valves in that QD.
Alls well, now I have spare parts
Anyone in need of a loader control valve?

 

[JeffWebb]

Yeah, that is what I was getting at by asking him to clarify what he meant by "full pressure to both sides of the cylinders at the same time."

Yes I replaced the loader QD’s
Yes the bucket operated fine.
Apparently the QD in the back is the return and was not allowing either side of the cylinder to release pressure.

Problem solved!

 

[JWR]

Great news ! This really was a puzzler.

 

[oldnslo]

Yes I replaced the loader QD’s
Yes the bucket operated fine.
Apparently the QD in the back is the return and was not allowing either side of the cylinder to release pressure.

Problem solved!

Actually I suspect your loader valve is a series - parallel model where the raise lower section return flow feeds the curl dump spool and or power beyond. This would explain full pressure on both sides of the lift lower cylinders and curl dump would work like normal.

That style valve makes lifting and dumping very easy to do.

A simple test: move joystick to raise at full speed and then curl and or dump at same time. Does raise function change speed when you curl or dump? If no then you have a series - parallel valve.