Does anyone know if the rear control valve can be rebuilt while it's still on the machine? Our machine is leaking out around the spools on the boom swing valve. Hoping it just needs new seals and o rings. BTW I have a manual on the way.
Also how do I release pressure on the system before disassembly other than lowering backhoe to the ground.
After shut down move all levers to release pressure on the system, you can due a lot of it on the machine, if it's leaking between the sections it has to come out.
Don't use hardware store O rings for replacements. Get genuine Case O rings, they have a specific dimensions for those spools. If you do remove the valve body from the machine replace all the o rings in all the sections. If you don't you will be doing it again.
Thanks for the advice tinkerer. I agree. Do 'em all once.
On a C the job is not complete unless the secondary valves and the load checks under thems orings are renewed as they are prone to the orings disappearing completely causing interaction between the systems , ie swinging when another circuit is pressurized or any other circuit moving without lever movement. As another stated, only Case replacements should be used as they are specially engineered for the application. Everything but section split can be done on machine but you will be very oiled up when finished, the boom will have to be moved side to side at allow all spools to be dropped.
ok, but how do you move the boom if the control valve is taken apart?
I do one section at a time, the boom can be supported and moved manually.
Great. Thanks for the info
get photos while doing the work........i noticed on mine that when i'm operating the boom it tends to swing to the left when fully extended. so i might need to do some work to the system down the road.
It's hard to swallow case oem prices. Can someone confirm that they used non-standard o-ring sizes? Has anyone used brands like parker and had problems? I don't have cross flow problems just bleeding off on the boom function. It's a 580D. It still digs fair but the machine won't hold itself up on the boom. I've got the spool exposed and trying to decide a full rebuild of the valve or just the boom spool. If I do a full rebuild I'll pull the assembly if just the boom I'll just try to fish out the one spool.
Your problem may not be the control valve. You may have seals leaking in one or both boom cylinders.
Does the boom leak down when in the transport mode? The boom down pressure relief is set to leak down when the weight of the machine is on it so the operator cannot cannot get into a dangerous situation by sitting the machine way up on the boom, they were weak enough that I set many up for customers so they could swing themselves over ditches. If the boom is not leaking down when raised but not locked, the cylinders and high pressure relief are ok, you can check the low pressure relief as it is set lower than system pressure, put a gage in the normal test port at the loader control and at a slow enough engine speed to prevent stalling push the boom down and read the gage. Let me know how you do on that test. The problem with off brand orings is the durometer rating, not sizing, the OEM rings were originally a whitish hard oring, I do not know how much the orings cost anymore but I would put the best available rings in there, they are not that much fun to do, let alone redo. Can you PM me with your phone number
Thanx for the quick replies. Yes the boom leaks off until it sets on the ground. This leads me to think its leaking off at the spool. If it was just the packing it would stop when the pressure equalizes in the ram. If that's not correct please let me know. I didn't know the pressure set was lower on the down side, thanx. The leak off is something that has developed slowly. I'm waiting on test gauges. Got some stuff thats gonna take me away from this for a couple weeks. Hopefully I can get the troubleshooting done tomorrow and if necessary parts ordered. Swinging on and off w/o moving back and forth on the wheels is the thing I do. Lazy yes but often the fastest way to position. Yeah don't like doing things twice. I am pretty sure I can get the durometer spec for the parker kits I have. Not so sure case will share them.
Any hydraulic cylinder with leaking gland seals will extend or retract as long as there is a force (weight) against it until that force quits or becomes neutral. If your belief were true, booms wouldn't go to the ground when a machine is shut off with the boom raised and unlocked (if it had a boom lock).
Thanx Tinkerer. I think we are on the same page but there are details that I omitted for the sake of time. Once equalized yes the load would continue descending due to gravity but with a small leak it would be at a slower rate. After the schooling from melben I am thinking my problem might be more due to the lift prv. But it is an old machine and I am sure leaks a bit throughout the system.
Tinkerer, it depends on which way the piston is going whether a loader will leak clear to the ground with a piston seal leak. if the spool on the top side of the cylinder is not leaking and the piston is moving down into the cylinder the volume mismatch from the presence of the rod will allow pressure to build till the loader will quit lowering. this can easily be diagnosed as putting the loader lever in raise with the engine stopped will open the return port to sump and the loader will leak down. If the rod is pulling out of the barrel as on a boom circuit, those conditions do not exist and the rod pulling out will allow oil to transfer due to the small volume leaking into a larger, the pressure can never equal.
Heads up on rebuilding the block. Found it best to just remove it from the hoe. And yes, OME orings should be used.