Hydraulics theory and operation

[Girdlebug]

I bought a l245dt w/ a FEL a month or so ago and have been lurking in the shadows since then using the vast amount of knowledge here to remedy quite a few issues. However, one still remains - the weak 3 point lift. It seems like there are lots of threads as this seems to be a common issue, and most get resolved fairly easily. I've slowly worked my way through suggestions to remedy the weak lift, but still have the issue. I'm really new to working with hydraulics, but am slowly gaining knowledge. So I thought I would ask for help both in understanding how the system works, and any suggestions on how to proceed.

From what I understand (in a nutshell) from the hydraulic pump on the right side of the engine, there is a supply line to the same case the 3 point linkage is connected to (not sure of proper name, directly under my seat). From there, is supplied to a small block under the left side of my seat. Two hydraulic lines are tapped into this block and feed the FEL, it's my understanding that one supplies pressure to the FEL and the other sends pressure back to the manifold block from the FEL when the FEL is not in use... it's that pressure that would lift my 3 pt hitch. There is a relief valve on the block manifold i'm describing and the FEL control seems to ahve one as well. Is this correct?

That said, onward to what i've done thus far to try to fix the issue.

- drained tranny/hydraulic fluid and purchased new hydraulic filter. The old one was totally gummed up, and collapsed. New fluid and screen installed, somewhat of an improvement. Will now hold the weight of my back blade - still will not lift.

- cleaned vent tube. Blew it out w/ air compressor. Vent tube is clear, but looking in the vent tube hole with a flashlight - it looks like there is still quite a bit of gunk within the case?

- cleaned relief valve on manifold block next to seat the best I could. Can I verify it's function?

- cleaned relief valve on FEL controls, this one was different than the one on the manifold block, more of a self contained cylinder. I could open the valve with a small file by pushing on it.

- blew out both lines connecting from manifold block to FEL controls.

So, that's where i'm at - the FEL works fine, maybe a bit slow. The 3pt lift will not lift on it's own, but if I lift the implement manually it will hold the weight.

Anybody have suggestions on what to check next, or steps to revisit?
Thanks!
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[Girdlebug]

I pulled the hydraulic cylinder cover today to inspect the inside of the vent tube and the o-rings on the hydraulic cylinder itself. The o-rings were fine both on the cover and on the piston within the cylinder. However it looks like something, maybe a piece of metal might have gotten trapped between the piston and the cylinder and scored the outside of the piston and the inside of the cylinder. How easily should that piston slide by hand within the cylinder? There's a few rough spots and I'm wondering if the piston is not traveling the full distance within the cylinder or maybe fluid is traveling through the score marks? Any thoughts?

Thanks, DH

 

[Lil Foot]

I would suspect the score mark in the cylinder is is allowing fluid to leak past..... if it was binding on rough spots enough to overcome the hydraulic pressure, you'd never be able to move it by hand. In my B7100, the piston o-ring also requires a backup ring for support.... mine was missing the backup ring & would lift, but not hold up my box blade. A new o-ring & backup ring & it works like new.

 

[Girdlebug]

Thanks for the reply. Did the damaged o-ring on your machine affect the operation of your FEL?

Both the back-up ring and o-ring on the piston both seemed to be in decent condition on my tractor - no tears noted.

 

[Lil Foot]

Thanks for the reply. Did the damaged o-ring on your machine affect the operation of your FEL?

No, but they are completely separate systems on my B7100....3pt is powered by the tractor's internal hydraulics, & the FEL is powered by an external pump connected to the front of the crankshaft.

 

[Girdlebug]

Re: Hydraulics theory and operation (getting closer)

Ok, I think I'm almost there but wanted to get OTT's thoughts on this.... Soi was planning on diving into the rock housing once again to check a few things when I thought I might just try on thing before draining the hydro fluid again.

My fel taps into a block (or manifold, or whatever) right below the left side of my seat. Here's a picture.



Notice I disconnected the FEL supply and return, and just routed an old hose I had on hand to those connections, thus removing the FEL control and circuit. I fired up the tractor and the 3point lifted like a champ for the first time since owning this thing.

So I think I'm missing something obvious in the FEL controls, like a relief or poppet or something that is robbing the return line that goes back to the block of it's fluid? I've blown out both the supply and return lines with a compressor. Any ideas? I'm open to any ideas...but at least have it narrowed down to the FEL.

I've posted pictures of the loader controls in replies below because I couldn't figure out how to post multiple pictures.

 

[Girdlebug]

Front of loader controls

 

[Girdlebug]

Rear of loader controls

 

[manofaus]

perhaps one of your loader valves has a closed centre spool in it and its stopping the hydraulic fluid to pass through your FEL valving to operate your 3 point. Could then mean that the FEL valve has been plumbed into the wrong ports on your machine, and it should be plumbed in so that one of the lines dumps back to tank.

 

[manofaus]

der...
but I suppose if that is the case then your hydraulics would need to go over a relief all the time.
So...
I think your FEL valving is closed center, and your hydraulics are going over the relief all the time. To rectify the problem you need open center valving on your FEL hydraulics so the only time you go over the relief is if you stall an operation on your FEL or 3PT.

To test you need to fit a gauge on your two lines that come/leave the tractor and see where the pressure is. With the FEL valve inactive and if its a closed centre you should only get pressure on one hose. If its open centre you should get the same reading on each line.

Or you could feel the lines... stop the tractor flick your levers to get rid of residual pressure and feel the lines, they are hopefully flexible. then start your tractor and you should be able to feel where the pressure is by the stiffness of the hosing. the hose will stiffen or move under pressure. If one hose from your tractor goes stiff then you know its got pressure.
argh..... or someone alot wiser will tell you straight up....

 

[eserv]

You have two lines coming from the right side of the loader control valve that return to the tractor. where do they each go? If you disconnect them and start turning the tractor engine from which one of them does the oil flow? That one needs to connect to the block where the two lines come from the tractor and the other one must return oil directly to the transmission case. (usually a fitting added to the transmission fill port)

 

[MagKarl]

I have the same tractor and loader. My loader supply and return also come to/from the block under the seat. For some reason your control looks to have more hoses than mine does. Where do all those hoses go? I wonder if some hoses are misrouted or otherwise limiting the return or loader bypass flow. I will go look at mine more closely this weekend when I have some daylight to work with.

 

[Girdlebug]

Manofaus, thanks for offering advice. I'm pretty new to all this, but just did a quick study on open vs. closed valving. So if I'm understanding correctly, if the valving is closed center, the pump would continue to supply pressure and the relief would activate dumping fluid back into the tranny case (if the FEL controls were not being used). Could the relief be stuck open? Would the relief valving be that cylinder on th rear left of the controls?

Eserv, one of the two lines on the right of the control returns back to the block in the first photo. I'm assuming this would be my power beyond? And that would power the hitch. The other line goes to the top of the tranny case, dumping fluid back into the resivour. The supply line to the FEL control is disconnected right now, so I haven't tried cranking the motor with return lines disconnected to see if fluid comes out.

Magkarl, the four vertical lines goe to the cylinders on the loader. The horizontal lines are as follows: left one is supply in from the block, right bottom is supply out back the block, right top goes to top of tranny case.

Thanks!

 

[manofaus]

if you stall out an operation on your loader will your 3pt work?
Your relief is usually straight after the pump so if you had no functions that would tell me that you had a stuck relief.

 

[Girdlebug]

There's a relief on the block, I was just wondering if the control would also have one?

 

[bky]

I have the same setup. with the same amount of hoses. and I believe your loader vale is indeed a open center valve. I and wondering if your loader controls might need rebuilt
I know I had to replace o rings in mine. also I had to replace the ball bearing on the left lever to make the float option work on my loader.

 

[Girdlebug]

Yeah, I'm not sure what's going on... I tore into the controller today, replaced the o-rings on the relief and cleaned it up. Still acting the same, loader works no hitch lift.

The controller is marked victor fluid power corp, but I couldn't find any literature on the controller. Did you just tear into yours and rebuild it yourself? Or did you take it somewhere to be rebuilt?

Thanks in advance - DH

 

[bky]

I just tore into it. if you do watch out for the bearing on the float side so you don't lose them. there is not much to it.

 

[MagKarl]

I went out and checked mine and do in fact have less hoses than you guys. I don't have a hose that returns to the sump. I have 6 total, 2 from the block to the loader control, and 4 from the control to the loader cylinders. What is the purpose of the line dumping back to the sump?

 

[Girdlebug]

I spent more time on the controller today and pulled the spools. Things look pretty good in there. It did get me start thinking about how fluid moves through the valve. I'm beginning to wonder wheather the PB lines are hooked up to the correct ports on the controller. The two lines (horizontal) on the right side of the valve look as though have direct access to each other's fluid, i.e. you can see directly to the other when looking within the valve. Should this be the case with the tranny return and the powerbeyond? It seems as though if the pump was supplying pressure to both the PB and blobk return lines, you wouldn't have enough power to operate the hitch.

Eserve, you said I should be able ensure the correct line is connected to the block by turning the engine and connecting the one that oil comes out of to the block.

Any chance someone with the same control could verify wear their hoses are connected? In my first photo the horizontal lines are as follows: left one is supply in from the block, right bottom is supply out back the block, right top goes to top of tranny case.

Mag, I'm not really sure what the return to the tranny is for...

Thanks everybody - I really appreciate it.