Hydralic lift problem

Spina · Nov 5, 2006

I have a B7200DT with a front loader.

The front loader has been performing inconsistently.
Usually works fine after the tractor has sat for a period of time (1 day to several weeks). Also works fine if I don't work it to hard. However; when I work it hard for any period of time the power drops. It starts by being slow to lift heavy loads and eventually will not lift the bucket itself.

I have done what I think is the obvious stuff; check levels change fluid and filter. Tighten fittings.

Any suggestions on a sequence of actions I should take. I prefer to be able to at least diagnose the problem or even fix it prior to giving it up to one of the local dealers.

KennyV · Nov 5, 2006

Is the 3 point still working when the loader quits? What is the temperature of the hydraulic oil when it quits working, and do you have power steering? KennyV.

KubotainNH · Nov 5, 2006

Mine stopped working on my b6100. The 3ph also stopped. I found the pressure relief valve in the FEL controls got stuck open slightly. I bet yours sticks open and then eventually closes back by itself. It's easy to check/fix, it's on the back corner of the controller. If I remember correctly you remove a cap, then remove an allen screw which contains the valve. There is a spring that puts pressure on a cylinder inside a sleeve in this valve. You should be able to push it in with a good amount of pressure. It should slide back easily by itself. Mine would stick until I cleaned it. There's a post I opened here about it last year.

Spina · Nov 5, 2006

No power steering.

The 3 point does keep working when the loader quits; sometimes I use a rake or a tiller. But the loader will quit even when I ensure no power goes to the 3 point.

I never thought to take the temp. Are there guidelines to what the norm vs. max temp? Certainly the machine is hotter when the problem shows up.

Is it typical for pressure relief valves to intermittently be defective over temp?

wushaw · Nov 5, 2006

Spina said:
No power steering.

The 3 point does keep working when the loader quits; sometimes I use a rake or a tiller. But the loader will quit even when I ensure no power goes to the 3 point.

I never thought to take the temp. Are there guidelines to what the norm vs. max temp? Certainly the machine is hotter when the problem shows up.

Is it typical for pressure relief valves to intermittently be defective over temp?

When the temp increases the oil gets thinner and if your pressure relief valve is sticking open then the fluid will pass through easier.

KubotainNH · Nov 6, 2006

Hmm, maybe it's time for a spool rebuild. There's alot of o-rings in there. If the loader stops working because of the relief valve in the FEL controller then I would think the 3ph would stop working too, or at least have very little lift strength. This is assuming it is the same setup as the B6100's. The output from the FEL controller heads back to the 3PH on mine so any loss of pressure to the FEL affects the 3PH. I posted some pictures of mine on this thread: http://www.tractorbynet.com/forums/kubota-owning-operating/70830-b6100-picture-2.html

MadReferee · Nov 6, 2006

Spina said:
The 3 point does keep working when the loader quits

This indicates that the loader relief valve is working correctly. If the relief pops then fluid is directed to the tank port instead of the power beyond port.

Do the hydraulics howl when the loader joystick is activated and nothing happens? Does the engine grunt? Does the 3pt lift at the same speed when the loader is working and also when it is not?

Spina said:
I never thought to take the temp. Are there guidelines to what the norm vs. max temp? Certainly the machine is hotter when the problem shows up.

Is it typical for pressure relief valves to intermittently be defective over temp?

I doubt temperature is your problem because if it was then the 3pt would be weak also.