FEL bucket goes spongy after warming up

[OldTrix]

I have a Mahindra 2665 that I bought with about 250 hrs on it. I notice that when cold, just after starting, the bucket curl is firm, as in I can drop the bucket down and then lower the loader and lift the ft end of the tractor off the ground. A while later, when warm, I can tilt the bucket down and lower the loader and the bucket just curls up instead of holding firm like it did when cold. It does stop and hold, but only after it curls up about a foot or so. I can apply more force to the bucket to uncurl it again, but I'm puzzled why this occurs. Usually, hydraulics will hold a given position unless the force is such that the relief valve gives way.

I've done the usual full travel/hold bleeding techniques to both loader and bucket, but that doesn't change anything. Cracking the lines open at the cylinders did not show signs of any air escaping, and I see no obvious leaks or any issues with the hydraulic lines.

Any thoughts on likely causes?

 

[OldTrix]

I will add, there does seem to be something off with the loader joystick. The uncurl function isn't as linear as the others. It seems to have two speeds based on the joystick position. All the way over is slower than 3/4 the way over. it behaves as expected until you pull it hard right. Maybe the cables need adjustment?

 

[oldnslo]

That model may have the regenerative dump option which speeds up the dump by 30 - 40%.

Soft or spongy normally indicates that air is getting into the system but I would expect this to more of a problem when oil is cold vs hot. Any rubber hoses on the inlet or suction side of the pump? If yes check any clamps or fittings to verify they are tight and inspect the hose for age cracks and squeeze to see if feels soft and spongy. Should be rigid and difficult to squeeze.

Do you hear any sound changes on the pump or system when working with cold oil vs warm or hot oil?

 

[OldTrix]

No real changes. If it's really cold, like in winter, the pump will be a bit whiney at first, but nothing too unusual. Nothing different on summer days. The hoses all check out. The pump routes to the loader valve via typical hyd hose, with PB headed back to the rear remotes. 3rd function hoses are also fine and routed correctly. It does act like air gets in there somehow, yet the next morning its solid as a rock again.

 

[oldnslo]

Off the wall thought but can you check the temperature of the pressure line to the loader valve vs power beyond and tank. If, repeat if there is some type of restriction in the flow path it might aerate the oil over time which would then settle out overnight. Checking for heat rise in those lines might show you if the power beyond or tank line gets hot quicker than the inlet. Again off the wall but gotta start somewhere.

Does 3 point lift a load same as always? If it also gets soft with hot oil that would kind of support oil getting aerated.

 

[OldTrix]

I'll play with that later today- I've switched to the grapple for rock collecting, but can at least give it the feel test for temp.

TPH has never been a problem, always lifts, never sags.

 

[Mike1955]

Another opinion, sounds like the cylinder leaking through. It is worse when warm. Just what I’ve run into on my stuff

 

[OldTrix]

I would think a cylinder leak would be a slow release. This acts like an air bubble, it gives a certain distance then, stops hard. Unless a certain section of the cylinder is damaged?

 

[Mike1955]

Well you might be right. This was a single action cylinder I just replaced. I replaced it, was only 2 hundred something, instead of packing. Faster can get back to work.

 

[OldTrix]

No real difference in temp that I can feel. My Backhoe runs off the rear remotes, and it seems to work OK, too. WHen i have the remote valve switched on to run it, I can hear the fluid running through it, sort of a hissing sound.

I'm beginning to wonder about the whole loader at this point. Running the grapple, I notice even the loader arms have give in them. Try to press down around a rock, and if it slides off, the loader drops a couple feet. It also lifts unevenly at times, twisting the whole loader frame.

I also notice the third function doesn't hold pressure. Grabbed a rock, curled it under (the top jaw is much longer than the bottom on my grapple) to hold it, and I could see the jaw slowly opening up. Had to hit the button every 5-10 secs to keep it clamped tight.

It really acts like there's a lot of air in this thing, but running it full travel each way, It seems to cycle ok.

Would a flaky pressure relief valve do this? I do have a gauge I can pop in line to measure pressure.