I have a Cat 420d backhoe that had issues with the loader bucket up and loader tilt where they would run weak and slow and stop or just not function hardly at all. Loader down and tilt (forward or backward I cannot remember as I have been spread thin and this project was put on hold) function normally as does the rear bucket. Because the two functions that were not working are beside eachother I assumed that I must be losing pressure between them on that side of the valve section. My initial thought was to just replace the two sections that aren't working correctly and be done with it and reseal the rest of the bank instead of trying to figure out if my spools are bad or if it was seals or maybe relief valve. It seems unlikely to me that I would have two spools go bad or two relief valves which makes me lean more towards it was a seal issue but this equipment was already out of service when I came here so I don't know the history of the problems and when they started happening. At this point I have thought myself in a circle and if anyone has a thought i would be grateful
No seals in the pressure side of the control spools (of consequence). I've repacked quite a few of my C & E backhoe front cylinders, even at lower hours (under 3k). And, the odds of two circuit relief cartridges at the same time, on two separate circuits? The primary relief, maybe? I believe the main relief would affect both the front and rear booms, though.
The mechanic before me ordered new lift cylinders before he left and I installed them that was when I discovered for myself that the tilt function was not operating correctly in one direction as well. Operating two functions and or reving the engine doesn't make much difference either. So with the rear controls working fine it seemed to me that it would have had to be in the valve somewhere. Between the cylinders and the valve there are no other reliefs just goes from cylinder to the control valve respectively. I pulled the spool out for the lift function and didnt see any damage to speak of but at this point I am not real sure what else it could be but to just replace the valves
It sounds like you may have a problem in the resolver circuit. There has been lots of discussion on this previously. Search the forum for the word Resolver.
Thank you for pointing me in the direction of the resolver. I pulled them out of both controls and both had blown rings.
Just to update I pulled the bank for the front of the backhoe and resealed the sections and once I pulled the resolvers and check valves I found that the orings for reaolvers on the tilt and raise sections had missing I rings so I replaced them accordingly. I reassembled everything and reinstalled on the machine and with no bucket on the machine the loader lifts just fine, but if I put a bucket on the machine would not lift it more than a foot or so. Checking the pressure at the test spud at the compensator on the pump I noticed running through the functions for the loader coontrols that the pump would never stroke more than maybe 350 to 500 psi for the lift function and when I would use tilt the psi would almost bottom out at 0. If I used the rear controls simultaniously with the front the pump would make the correct pressure and the functions for the loader would work fine. I am just unsure as to why I am not getting the signal for the pump to stroke from using the front controls only and why my pressure is almost 0 when i use tilt. None of the functions on the front of the backhoe will signal the pump to stroke higher pressure so now I am lost once again. Would the rear controls having blown orings on the resolvers cause these symptoms or should I just stay focused on the front bank? I am just perplexed as to why I cant get the pump to put out on any of the functions for the loader.
First, can we agree on some terminology? Let's call the front controls the Loader Controls, and the rear the Backhoe Controls, just so everyone is on the same page. Second, yes, a fault in the backhoe controls can affect the loader controls. Third. Systematically go through each function in turn and record the pressure when each function is stalled out. (That is, the cylinder is held at the end of its stroke) Don't forget the steering. Fourth. What's your serial number.
On the front controls the pressure is about 350 to 400 with everything except the tilt forward which drops to about 50 to 100 psi. The sserial number is crs11055. Vin is cat0420djbln11360
What about the rear controls and the steering.? Because everything in the hydraulic system is inter-related you have to test every one of the circuits in turn, not just a few of them. BLN11360 (the last 8 digits of the PIN) is the machine Serial Number. CRS11055 is actually the engine S/N.
Steering only showing 350. Rear controls about 2000 to 2200
When operating the backhoe controls, did you include the stabilizers. if not, operate the right and left stabilizer and the loader controls at the same time, The right stabilizer has the last resolver before you operate the steering and loader controls
When I operated the stabilizers and the front controls I did not get any increase in pressure. For the rest of the rear controls I do but none with stabilizer unless I operate another rear function with it. So I should look at the resolver in the function before the stabilizers which in this case would be the e-stick
Did anyone ever solve this im having pretty much the same issue on my 420e I've got next to no pressure across the whole system including steering stabilizers and front loader, I did replace the tilt cylinder with a new one as the previous got bent in use
Sounds like a pump.