790/300 loader hyd. issue when going down

[Phineas7]

<<Sorry, just realised I posted in the wrong forum!>>

I've got an odd problem. I suspect something in the valve. It loads the engine to go down with the loader. Up is fine, bucket movement is fine, 3pt hitch and T&T all work normal. With the engine off, going down barely moves. It just slowly creeps down.

I did change the hydraulic fluid a few hours ago. It seemed to happen just from one day to the next. Nothing really stands out as "happening" to the loader. I wasn't even using it. Just lifting it up off the gound for some BB work.

Any thoughts?

Regards,

P7

 

[kennyd]

Check the QD's, unplug each one and then re-connect. I'd almost bet one is not seated all the way.

 

[GREENCO]

CHECK LOCK OUT LEVER ON LOADER CONTROL LEVER

 

[Mech]

If it goes down normally when pushed into float then it isn't anything mechanical binding so, as Kennyd said, it must be something blocking flow in the hydraulics.

 

[Phineas7]

I did check the lock lever, seemed ok.

I don't think it's anything mechanically binding because it acts the same regardless of where is in the stroke and I'd expect to see some sort of twisting of odd movement if it were.

Will definitely check the QD'd when I get home. It would be easy to kick one what getting on.

Now that I think about it. I should be able to swap the lift and bucket lines as a test. If the problem moves to the bucket, it's in the valve.

 

[kennyd]

Sure you can swap hoses...but just re-seat the QD's first. There is nothing really in the valve that can go wrong.

 

[Phineas7]

I cleaned and re-seating the QD'd had no affect. I reversed the direction of the lift cylinders and noticed that there was some additional load when going up, but not as much. This would indicate the blockage is on the return circuit of the tractor side of the QD.

It's almost as if the spool on the return side it not working and that's it's working against the over pressure bypass.

I guess I need to pull off the front pannel to get a better look at the valve.

 

[prosperity]

I had the exact same problem with my 2520 w/200cx loader.

I also did the same as you did by switching the lines to isolate the problem.

It is the quick coupler - female end that is attached to the tractor.
When I called my dealer about this, he immediately said to switch out the coupler.

There is a spring and seat inside the coupler that gets cocked at a wrong angle inside - he said he has had a lot of these go bad lately.

 

[Phineas7]

ok, thanks. Had you ever disconnected your loader?
Until this issue I've never touched the QD's.

I'm going to try and talk to the dealer this week. It's a chain: They're nice guys and seem to try, but they don't appear to be the sharpest pencils in the cups. I've never talked to their mechanic though.

 

[prosperity]

ok, thanks. Had you ever disconnected your loader?
Until this issue I've never touched the QD's.

I'm going to try and talk to the dealer this week. It's a chain: They're nice guys and seem to try, but they don't appear to be the sharpest pencils in the cups. I've never talked to their mechanic though.

Yes - I've disconnected it a few times - shouldn't make a difference though. Mine didn't go bad right after a connect or disconnect. In fact, I was doing some loader work for ~3 hours when it suddenly had the same exact symptoms as yours.

My dealer said he has had a few of these go bad lately - must have been a bad batch. After I took the fitting off, and took it in, we looked closely at it, and couldn't see anything wrong visibly. But, I put the new one on and has worked perfectly since.

What happens is there is a ball, seat, and spring inside - the seat gets dislodged somehow then blocks the fluid flow.

Mine was covered under warranty - don't know if yours is or not, and don't know the cost of the fitting.

 

[Phineas7]

Very interesting. I'll definitely swap them before taking it in. It should be under warrantee. I've not had it quite a year yet. It's just a hassle to borrow a trailer and haul it there and back.

 

[prosperity]

Very interesting. I'll definitely swap them before taking it in. It should be under warrantee. I've not had it quite a year yet. It's just a hassle to borrow a trailer and haul it there and back.

That's a sure way to tell if the fitting is bad by swapping them. Remember it is the female end that is attached to the tractor that went bad on me.
The way that I did it was to just swap the lines as a test - reversed the up function and down function lines - then the loader would not lift at all (engine struggling), and the down function worked fine.

I didn't take my machine in - just brought the bad fitting in and they gave me a new one.

 

[Phineas7]

I swapped the females as you mentioned and the problem moved.

After inspecting the faulty connector from the back side I could see the circlip that held the internal valve in place was out of it's proper groove causing the back side to be back farther than it should be and cocked.

I re-seated it and put it back on. So far so good. I suspect is was never properly assembled, at least I hope. It's one of those flat ones with the beveled ends, so that when it's fully seated, it makes a nice surface all the way arounds and the beveled ends are touching.

As to why it caused the problem, I have two theories, but I'd have to disassemble it to know. I figure that it could be that the cocked backing was causing it to bind and when the male is connected its poppet was opened extra wide and the female was barely opening.
My other theory is that the poppet on the end is not actually the valve, but a cover for the valve. The circlip would hold the actual valve assembly and the valve assembly would be moved back farther from the poppet when the circlip was unseated. This would cause the poppet to be un-able to fully open the valve. I say this because pushing against the spring from the back felt really week. I suspect there are two springs, one for the poppet and one for the valve.

Regardless of all that, thanks so much for you excellent advice!

 

[prosperity]

Glad I could help.

I never looked that close at my fitting - I figured it was under warranty, so let them just give me a new one.

If these fittings were in fact assembled wrong, I wonder why it took ~40 hours to surface?

Anyway, glad you found the problem.