790/300 loader hyd. issue when going down

[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.