FEL bucket goes spongy after warming up

[oldnslo]

Lifting crooked would point towards potential of one of the lift cylinders leaking internally but that shouldn’t cause any sponginess and would expect that to a constant problem not only when cold.

 

[rScotty]

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.

You say it works good when cold, but not when hot. I can't think of any reason that temperature would cause such a problem. But a suction air leak certainly would. Instead of temperature as a cause, we are looking at the time the tractor is running...same thing. The amount of entrained air would increase as the tractor warms up. Then the hydraulic fluid would give up the air overnight as it cooled.

Hoses aren't the only places that can cause a suction leak. Connections are known to be a problem, and the hydraulic pump itself can pull air past its seals. It seems to me that all your symptoms point to a suction air leak somewhere. First thing would be to check the fluid for air.

Simply take a sample of the hydraulic fluid after it warms up and the problem begins...maybe use a syringe or turkey baster to pull a sample of fluid from the sump and put it in a glass jar with a loose lid. Entrained air makes the fluid yellow and opaque, but it clears up after sitting overnight.

Another way that is more work..... but you could put a section of clear tubing into the FEL return line. Then you could see the fluid in real time. Might want to check the return line pressure with your gauge first, & maybe put the clear section closer to where the return line enters the sump...just in case it leaks. But that's your call. Hardware store clear vinyl or polyethylene tubing will handle 50 psi easy. Barbed fittings with worm drive hose clamps will too.

rScotty

 

[Mike1955]

Oil trim I don’t think a relief valve would cause that effect. That machine definitely has a lot of wear in the cylinders and the bushings and the control valves And the oil has possibly lost some of its viscosity. Add it all up and you get a little instability.

 

[OldTrix]

I know the grapple is solid as it's only 2 yrs old and was fine on my old tractor. The slow bleed down of the grapple jaws points to a leaky 3rd function valve in my mind.

I had the loader off the tractor last week and looked at all the couplers and fittings. Nothing appears to be leaking externally, so I think the coupler o-rings are OK.

I'll chase the suction lines next and see what I can find. I'll also pull the strainer to ensure it's not plugged up.

 

[rScotty]

I know the grapple is solid as it's only 2 yrs old and was fine on my old tractor. The slow bleed down of the grapple jaws points to a leaky 3rd function valve in my mind.

I had the loader off the tractor last week and looked at all the couplers and fittings. Nothing appears to be leaking externally, so I think the coupler o-rings are OK.

I'll chase the suction lines next and see what I can find. I'll also pull the strainer to ensure it's not plugged up.

It's easy to tell if you have a suction air leak. Cold hydraulic fluid that has set overnight is clear.

If you pull a sample of oil from the sump when it is hot and you see that the fluid is still clear like it was when the fluid was cold then the tractor doesn't have a suction air leak problem.

But if the hydraulic fluid has air entrained in it the fluid will look cloudy like this photo. Fluid that looks like that is filled with microbubbles of air and will cause the cylinders to be "spongy".

 

[OldTrix]

Well, I think I may have identified a potential source. I've been out all day, moving some deadwood, rocks, etc. with both the grapple and the backhoe. Figured I'd take a shot at a stump I want gone just to chew up an hour or so. Tractor has been running fine all day. Set up and start digging. I usually set the engine around 1100-1200 RPM for backhoe work, which seems to do the trick.

After about 15 min, I turn around and notice black smoke Uh-oh. Thinking it may be loading up, I rev it a bit, it doesn't clear. Black smoke turns to white, and the next thing I know it's on a runaway! Stall it, and ponder what's going on. First thing I do is check the dipstick. I had changed the oil 15 hrs ago, and check it every couple of days, and it was fine yesterday. The level on the stick is completely full. I think the pump is leaking into the crankcase somehow, which would explain some of the hydraulic problems I've been having.

Thoughts? Where else could the motor suck in hydro fluid? It's a gear model, so it could be worse. Hopefully the motor isn't toast. After it cools, I'll drain and refill the oil and see if I can move it.