Hi folks, I'm new here. Looks like a good place to get some answers. I've got a Kubota tractor with a BushHog M446 loader on it that has recently developed a problem. It won't lift at idle or low rpm's. The rear lift works fine. The bucket rolls normally. It will lift but I have to rev it up to about 1500 rpm or more. The fluid level is ok. Shuttle shift works fine and power steering is ok. The tractor is 10 years old but there's never been a problem and the loader has never been off the tractor. It has a Walvoil joystick control valve. I've taken out the pressure release valve and saw no obvious problems there. I've swapped the lines that roll the bucket with the lift lines and that made no difference. Any ideas?
I am no expert but might want to hook up a pressure gage.
Does the loader lift settle in the neutral postition? Simplest explanation is a blown piston seal. The internal leak will create heat that you should be able to feel. You can hold in the lift position for 30 seconds and go feel the cylinders to see if you can find a warm spot, if not run it a minute then try again. There are other methods to determine which cylinder is leaking if the loader won't hold and it's not the valve, which it sounds like you eliminated.
The loader does drift down a few inches if I stop it as it comes down. I haven't checked for hot or warm spots on the cylinders. I did try disconnecting each cylinder at its attachment point to see if the problem might show in either cylinder but each one would raise the loader. I've been told that I might have to cap off each cylinder individually. Sounds like the easiest check right now is to check for warm spots.
what is the model of the Kubota?
It's a M8200