L5240 3pt won't raise

[dtreid]

This tractor had a piled-up hydrostat that I rebuilt. Has been working greatfor the last 20 hrs.

Went to use in today and the 3pt won't raise. The control lever is moving what it should but there is no movement in the 3pt hitch. If I lift it up manually, it will stay up.

Hst, power steering, and loader works normally.

Any ideas?

 

[bczoom]

Are there any safety items on the tractor that limit when the 3PH can be used (or not)?
When sitting on the tractor seat, is there a knob between your legs that controls the speed of the 3PH movement? Have you tried turning that in or out a bit?

 

[dtreid]

No safely limiting devices. The speed control knob works as it should, but doesn't have any effect on the hitch not raising.

 

[dtreid]

With no weight on the 3pt, it will slowly come up if the engine speed is set high. I noticed at idle, when cold that the loader jerks a bit when trying to raise. I'm wondering if I have some plugged hyd filters? Only 20hrs on the oil since I repaired the hst, but perhaps it's flushed some more junk out of the system...

 

[dtreid]

Changed the filters and no difference. About 1600rpm the 3pt will come up slowly, but if I stand on it, it won't come up.
At full throttle, it comes up quickly. At idle, it won't move at all.

Took the check valve and safety valve out of the control valve and everything was clean. Still the same problem.

Noticed that if I move the loader down at 1600rpm, the 3pt comes up quickly.....

Any ideas?

 

[Fedup]

I can't help but wonder about your timeline here. You rebuilt the hydrostat twenty years ago and it's worked fine ever since? The oil has twenty hours on since then? The problem with the three point is new? The jerk in the loader is new as well?

Maybe you can fill in a few of the blanks as to what's been done on/to the tractor recently.

The part about lowering the loader and the lift goes up raises questions about the loader plumbing.

 

[dtreid]

I purchased the tractor with a hst that was ground up. Pulled the tractor apart and replaced the hst pump and motor.

Have put 20hrs on the machine since the repair

Just the other day the 3pt would only go up if the engine was at 1700rpm or higher.

I changed the hyd filters. No change

Removed the relief and 3pt safety valve. They weren't dirty. No change.

Just pressure tested it and can get 2700psi out of it.

If I put the loader down while the 3pt is coming up, the 3pt moves up a little faster.


This is where I'm at. Any ideas appreciated

 

[Fedup]

So the tractor was inoperative when you first got it? You don't know if the lift or the loader was working properly at that time?

Does the loader have a dedicated two spool valve, and if so, how many lines connect it to the tractor hydraulics? Two or three? Let's start there.

 

[dtreid]

The tractor did still operate when I got it, just not well. The loader and 3pt were working.

After the repair, everything worked perfectly until the 3pt stopped raising.

The loader does have a 2 spool valve. Oil for the 3pt is routed through it.

 

[Fedup]

I'm with you so far. Again, the loader valve. Two lines or three? Not a critical question, but does the loader valve plumbing look "factory", or more like homemade?

My thoughts so far lean towards the hydraulic pump might be sucking air, but I still need more information to firm that up.

 

[dtreid]

It's totally factory

 

[Fedup]

Once again, two lines or three? It does make a difference.

 

[dtreid]

2 lines

 

[Fedup]

I went back and read your first post, and must apologize for not getting it right to start with. You stated things worked right for twenty hours, not twenty years. My mistake.

Okay, thank you for the valve/lines update. A loader valve with only two lines, mounted between the pump and lift system has been a pet peeve of mine for years, simply because (in my opinion) it's the wrong thing to do. That being said, it's not your problem today.

So let's go back to part where lowering the loader affects the three point. With only two lines on the loader valve return oil from the loader cylinders has no direct path to sump as it does in the traditional three line "power beyond" configuration most loader valves use. Instead, the oil coming back from the cylinders is forced into the line leading to the three point. That oil could be what's causing the lift arms to raise faster while the loader is being lowered. This makes me wonder why the pump may not be supplying enough flow, and the problem may not be in the three point at all.

The 5240 pump has a single suction with two outlets. One for steering, one for hydraulics. Usually if the pump is sucking air, or has restricted intake, it will affect both pump sections and both systems.

You had the tractor pretty well scattered getting the hydrostat out and back in, so you're familiar with most of those lines, seals, and o rings. You would know if any were suspect that weren't replaced during all that.

Yet you seem to feel the steering and loader are working as they should, right? The problem is just with the lift arms? I think what I would try next is a simple air check. Lower the lift arms all the way down. With the engine off, move the lift controls to full raise. Remove the line from the exhaust/return port on the loader valve. Remove the transmission filler plug and then apply air pressure to the line sending oil flow the lift system. If the internal valve mechanisms are working the lift arms (with no weight on them) will pop up. On the other hand, if the system is bleeding off internally for whatever reason, the arms may make an attempt to raise then you may hear air rushing out the filler opening. If that's the case you can't blame the pump.

 

[dtreid]

It does have power beyond which supplies oil to the 3pt.

 

[Fedup]

I'm not buying that. You don't get power beyond with just two lines. That's not how it works. I know where there's a 5240 with a factory loader. I put a new engine in it less than a year ago. The loader wasn't attached at that time. I'm going there (possibly tomorrow) to work on something else. I will look at it, and see how it's set up. Maybe that will clear up the picture I'm seeing in my mind.

 

[dtreid]

There are 2 spools. So 4 lines go off the valve to the loader. There's another line for supply from the pump and another for oil to the 3pt hitch

 

[dtreid]

Got it fixed. Took the position control valve off and apart. The little screen had a hole in it so I guess it wasn't doing it's job. I took things all apart and cleaned things out well. Now it's back to normal.