Hi there I have a CAT320D. When I bring the stick in toward the cab it works fine and then it automatically goes back and straighten the arm completely as soon as the joystick is in neutral position. I guess the valve block. Could it be dirt or electrical? Please advise. Jakes
When the joystick is in neutral and the stick is moving outwards can you stop the movement if you move the joystick just slightly away from the neutral position in the "stick in" direction.? A machine Serial Number would help. There are lots of different models of 320D.
Hi there Yes, it stops and you can even pull it in all the way. cat0320dazbh00844 I guess valve spool dirty. Just need a few pics of it also. Jakes
Possibly a broken centring spring on the spool for the stick in the main control valve.? Before opening up the control valve it might be an idea to see whether or not there is any sort of a pilot signal coming to the main control valve stick section when the joystick is in neutral.
On my 322L years ago, the centering spring came loose on several spools.
With stick at midway, and pilot enable off, does the stick move? In other words, raise the boom a little off the ground, and shutoff machine. Restart the machine. Does the stick move before raising the safety lever?
Hi. I asked them to test it. Pulled the stick in so its vertical to the ground. Switched the engine off. Safety on, pointing to the floor. Start engine. Stick moves outward, away from the cab. The machine is 800km from me on a small mine. I live in Namibia so everything is far away.... I want to try to diagnose, so when sending someone they have a better idea of what the problem might be. Thanks
If the stick moves even with the pilot system deactivated then the main control valve spool is not in the neutral position. Just have to find out why.
Hi. So If I follow the front pipe/hose from the cylinder to the main control valve I can open the caps and check the spring, dirt and see if the valve moves freely?
Correct
It should be either #16 or #22 on the illustration below. Depends exactly how the machine is configured.
#2 has likely come loose. Loctite and retighten.
Hi there Thanks a lot to all. The valve was stuck. Some 1000 grid paper and cleaning sorted it all out. Regards Jakes
Could the spool have stuck as a result of contamination in the system.? Were all the implement hydraulic filters changed after the control valve was opened up and the spool issue was resolved.? Knowing Namibia it's quite likely that some dust could have got into it while it was open. Did anyone cut open the old filter element and look inside it for particles.? When was the last time the hydraulic oil & filters were changed.? Your sticking spool could possibly be an indication of larger problems to come.
We had one of the lock screws in the bucket cylinder that came lose and damaged the cylinder.. We replaced the cylinder, with new filters and oil. So, I guess that was the culprit.
That makes sense. I’d suggest to change filters after a short interval, cut them open and see what is in them, if anything. Also check any magnetic plugs/strainers/screens if there are any. If there is any sort of contamination circulating as a result of the issue in the bucket cylinder, your problems could become very expensive very rapidly.
Double post.
Thanks, will do.