I have Liebherr excavator that is having some hyd issues. I have narrowed it down to being hyd and not an engine issue. Issue is as follows: While trying to curl/dump bucket it wants to move very slowly, I can get it to move as normal by barely moving another function. When moving another function it makes the bucket function work like normal. I have narrowed it down to the bucket circuit obviously. It is the only function that has issues. The pump doesn't labor until stalling it in either direction. It doesn't seem to load the pump until it's stalled either, doesn't seem like it's wanting to bring the pump up on stroke while moving just the bucket. Anyone have any ideas? I don't think it's a pilot issue since everything else functions fine. Could be circuit relief? I don't think cylinder is bypassing or piston is broken. Thanks!
Anyone think is the secondary or circuit relief had a broken spring or is worn it would be lower than the main and dump pressure back to tank slightly thus causing a slow bucket function. Sound possible? Any other ideas?
You did not say what model you are working on, if the machine has a pilot control system (joy stick valves and hoses) I would go to the spool next to the bucket, say crowd, and switch the pilot lines form the crowd to the bucket. Start machine and work the bucket with the crowd hand valve and see if it changes any. The system could have a loose piston in the bucket cylinder, centering springs on the bucket valve spool loose or broken, pressure seal in the end cap bad, bad pilot hose from the hand control valve. The list goes on. I would try to get a gauge on the pilot line to the bucket spool and check some pressures if you can. I have not been around many liebherr machines in the last 20 yrs.. I think there is still a factory dealer outside of Raleigh NC near the Senter Sanders ford.
PS you may be able to switch the circuit relief on the bucket only top to bottom depending on you valve and see if the problem changes any. May be other members on here with more info on these machines that can help you more.
If it speeds up when you grab another function then I would be looking at the pump signal system for the bucket. Its not stroking the pump up. If it was a cylinder or relief valve in the bucket circuit moving another function shouldn't change anything. I'm not real familiar with liebherr but that's where I'd start on a cat
I agree
Okay sounds good. It's actually a material handler but pretty much just an excavator. It's a r934b it got a log grapple on it instead of a bucket. I will see what I can come up with Thanks for help!
A small bit of advice and something I know is the best method to try to stick to although I often leap into things that look like it might be the fault?? that is firstly check all the filters both feed (strainer) and return on pilot and main pumps, then check firstly the pilot pressure at low and high idle, then check the main pump pressure on P1and P2 if fitted by dead ending the cylinders, if its just the arm function at fault the swing and track pressure is not an issue to get involved with, if a main spool spring is broken the spool with act without pilot pressure most usualy( safety lever down) this is often overcome by moving the hand lever to activate the reverse action of the spool after the safty lever is deployed, also cylinder and pipe work heat usualy points to a bypass leak?? or failed check valve, the quick hitch if fitted can cause odd faults so can blades that are common found now on smaller excavators, the fact that the bucket service speeds up when another service is activated most likely bringing in 2 pumps depending on its mode setting as of CAT that can select priority on stick or boom your fault should be easy to trace. tctractors