Weird FEL behavior

83Ttype · Nov 9, 2019

I have been using a friends JD4300 tractor for the summer and the FEL has some weird behavior. I did a full fluid / filter change and it made no difference. It has a single control lever with front/back to raise/lower and side/side control the bucket.

When lifting the loader:

Full pull back on control lever, everything seems normal until you quickly stop lifting. The bucket then drops about 6 inches before stopping.

If you only pull back slightly on the control lever (0 - 12%), the bucket will slowly drop.
A little more pull (20-40%) and the bucket will stabilize, but not lower or lift.
More than 40% back on the lever and things seem to lift normally until you go back to the neutral position where it drops a few inches.

I switched the quick disconnects on the control valve with the bucket controls (bucket seems totally normal) and the loader behavior was exactly the same even though it was using a different control valve.

So I am totally stumped as to what to do to fix this. I do know that the tractor sat for over a year without being used and I don't know if it was doing this before I borrowed it. I want to have it fixed before returning to him but not sure what to look for.

RNeumann · Nov 9, 2019

That sounds like pretty classic cylinder seal failure. One or both of the lift cylinders will need some love.

RNeumann · Nov 9, 2019

Bypass testing a hydraulic cylinder - YouTube

wdchyd · Nov 9, 2019

Yep, RNeumann got it right, piston seal failure

Leejohn · Nov 10, 2019

Could maybe be the load check valve spring or seat bad.

ovrszd · Nov 10, 2019

I'll take the other side. I suggest valve failure.

ovrszd · Nov 10, 2019

The cylinders aren't very smart. They hold or they don't. If cylinder failure was causing the drift it might continue all the way to the ground. Only controlled by valve sensitivity. If valve is failing, nothing will control drift.

83Ttype · Nov 10, 2019

Leejohn said:
Could maybe be the load check valve spring or seat bad.

Would that still happen when I switched the hoses from the bucket valve? The behavior was exactly the same and would have been using the second spool. Cylinder seals are a lot cheaper / easier fix.

83Ttype · Nov 10, 2019

The loader did seem to hold the load fairly well once it had settled that 6 inches after lifting. I was moving dirt so it really only had to hold for a minute or so, but it wasn't constantly lowering itself down like I assumed it would if it was leaking past seals. Since the 2 cylinders are "tied" together in the hydraulic system, I figured it would slowly drop even if only 1 of the cylinder was leaking. It is a JD 430 loader and rebuild kits run about $50 per cylinder (parts AH157965 Seal Kit & H169904 Ring).