We have an old John Deere 750 We are trying to sell but we want to fix a problem with it first. It used to have more loader power but lately in the last year or two it really seemed to lose it and it can no longer pick up the front wheels with the bucket (unless we tilt the bucket down but that's different).
Now it just squeals and fails to do it. It also doesn't have as much up force. It can carry a load of gravel but that's about it. I live in a remote area so we are diagnosing this ourselves.
We started by getting a hydraulic gauge and hooking it up to the loader control output. We are making above the rated pressure at 2400psi and after the step-down 1200psi. For some reason these tractors have a pressure step down for just the bucket lift hydraulics. It's the block that's pictured, the one that isn't the controls. Anyway we measured in front of and behind it and it's doing the expected thing. It's also the thing that squeals when the machine can't lift any more. Which I assume is fine, I think that's just what those bypasses do when they are topped out.
So anyway as far as we can tell we have all the pressure we should have. I think all that leaves is something wrong with the pistons. Bad piston seals? Can anyone help us figure out how to diagnose that? I was thinking maybe if one of the sides was working and one wasn't, it would be acting kind of weak like it is. I could always try one at a time.
Anyway if anybody with hydraulic tractor knowledge has any advice for debugging this, I would love to hear it! Thanks. This is a great sub.
by light24bulbs
2 Comments
I think your looking in the wrong place. Check your fluid level, and check your hydraulic filters. If those check out then I’d check the output on your hydraulic pump.
The symptoms that you describe sounds like what happens when you don’t have enough fluid in the system, especially the whining. That’s usually a symptom of the pump being starved of fluid.
I would be very surprised if it’s a problem with the cylinders. When cylinders go bad they either blow seals or they physically break in a way that you’d easily see it. If they weren’t equalizing between the cylinders you’d see that. The loader wouldn’t lift levelly and would bind up if it was the case.
Check the fluid level. Any leaks? When’s the last time you filled her up? Pressure doesn’t necessarily indicate you have the proper fluid amount in the system