I recently bought a cat 420dit backhoe and discovered that pedal was sticking on the extendahoe . I checked the linkages and they seemed ok but the spool seemed stiff .I sprayed the area and worked on the pedal and almost had it free when I discovered the main stick started retracting on its own . Now I have two problems when I was trying to fix one .would this be related or do I have a bypass and if so how do I fix it ?
Sounds like you may have some sticky spools in the valve.Do the joysticks seem to be coming back to centre. You may have some debris moving through the valve. It wouldn't hurt to remove the hydraulic filter and cut it open to inspect it.
yes the joysticks seem to be centering .the pedal on the extendahoe is not centering .even when its centered it still extends on its own.The main stick retracts but it don't have much pressure if you don't use the joystick it will stop if you touch ground with the bucket . It has lots of pressure if you use the joystick
If the main spools aren't returning to neutral you will have to clean and inspect them for scoring. I'd sure be looking in the filter to see if there's any metal or cylinder seal material showing up.
took the hydraulic filter off today and found metal cuttings in it . now I know why the spools aren't centering .would the cuttings be coming from the estick cylinder .how do I check the cylinder to find if that's the problem and how do the cylinder come out from inside the stick . how do the spools come out .
From what you have communicated, I suspect that the e-stick cylinder rod is bent, and the piston is scraping the wall, thus the cuttings affecting mainly the e-stick. The e-stick valve segment is probably severely damaged and needs replaced. Other valve segments may also needed replaced. I would first remove the e-stick cylinder and determine the exact problem. I would next remove all valve segments, break each apart, remove the spools and other components, determine damage, flush, clean, repair, and replace as needed. For the e-stick cylinder removal, remove bucket, extend bottom/stick as horizontal as possible, extend e-stick, disconnect lines at top for e-stick, disconnect bucket hoses to bucket cylinder, remove bumper wear plates for e-stick, remove bottom bridge plate, connect e-stick to other loader or crane, remove top pin holding in e-stick cylinder, and slide out. Remove bottom pin in cylinder and remove from housing. Another guy on a recent thread just performed this removal. The valve segment cluster pulls out the top. Remove back glass, remove floor access panel, disconnect all lines, remove 4 top bolts, and pull up and out (leave control sticks attached). It is heavy so a crane type device is needed to reach in and lift. To break apart the valve segments, disconnect spool to control stick connectors, remove 3 long rods holding all segments together, and break apart each segment. Remove the bottom caps and pull the spools out the bottom. Your next step, flushing the entire system, will depend on what you find and the amount of risk you want to take.
Also take a close look at the bucket cylinder and stick cylinders, if any of them have a dent from hitting something that's probably going to be your culprit. And those two cylinders usually take the most beating externally. If you have gages available, you might want to check pressures, might help to isolate the circuit causing the issue.