cat BZY01578 Bucket curl is very weak. It struggles to close an empty bucket The pump pressure when trying to curl only goes to 125psi. NFC drops to about 70 psi pump pressure when opening the bucket goes to 4500 psi. NFC drops to about 70 psi Boom up both pumps go to 4500psi. NFC 70 psi Boom up and bucket open is the same 4500 and 70 Boom up and bucket curl NFC 70 and pump 1 pressure 150 I'm thinking either something broke in the cylinder or the relief valve for bucket curl failed? The pumps should be good based on the pressures when using other functions and NFC is telling them to stroke so control circuit should be good. Is there anything else in the system that would cause this? I'm not real familiar with cat hydraulic systems and I don't have a manual. Just going with my gut. All pressures were taken from the display on the machine in service mode and against the cylinder stops. Am I on the right track? I should also add the machine has a thumb and operators like to use the bucket curl and thumb close to break material apart. When the bucket closes against the thumb it does push the thumb back when there is no hydraulic flow to the thumb. But obviously when both circuits are working against each other not so much.
Does the bucket drift one way or the other when in the air doing nothing?
It will drift one way. If you curl the bucket closed it will drift open. If you open the bucket it will not drift closed.
A cheap quick and dirty check is to swap the circuit reliefs cartridges on the main valve body and see if the drift moves to the opposite direction. If not, I think I would probably pull the cylinder. Do you know if you machine has the position sensors in the cylinder?
I do not know if it has position sensors on the cylinder. There are no electrical lines that go to the cylinder so i would assume not? I was thinking i would swap hoses but cartridges would be faster. I will give that a try first.
No position sensors in the bucket cylinder on that machine John.