Hello All, Newbie here, but have been lurking on the forums for a while to try to learn and have found so much helpful info. Situation: 1986 Case 855d Tracked backhoe loader. 6400h. Amazing machine, cummins 6 diesel, NA. Thought I'd change the hydraulic fluid since I didn't have much history on the machine. After a lot of reading I went with TRIAX Agra UTTO XL. I had an issue prior to this where I tried to solve some minor weeping stabilizer cylinders with Lucas Oil hydraulic oil stop-leak. This turned my hydraulic fluid into some very strange orange colored fluid which could have passed on a plate for Chicken Tikka Masala. Not even kidding. Same consistency and color. Drained the system after running less than an hour with limited power, changed all the fluid and the main filter in the tank. Fluid now running is Triax. Looks clean on the sample I pulled from the res tank. Have been dealing with a gradual loss of power over the last 7h since fluid change. The puzzling thing is that some functions such as the clamshell bucket open/close and the loader tilt seem to function with normal power. Backhoe swing and bucket curl as well as the extend-a-hoe work so strong that I can pull stumps out with it. However I noticed yesterday that the loader lift function and backhoe pull-up functions barely work against gravity. Puzzling thing is that when I accidentally hit clamshell closed lever while it was closed you could hear the engine bog down in usual function and it seems that this action restores full power to the loader lift function while the clamshell lever is pressed. I've ordered the recommended hydraulic test gauge and will test pressure, as well as possibly change the fluid again, and also noticed the small mesh filter in the valve control inlet which I plan to inspect and clean. I'll test pressures and report back. I was wondering two things. 1. Where should I direct my attention in trouble-shooting, have I missed anything glaringly obvious and am I doing this in the correct sequence, as guided by the repair manual. 2. Is there anything that I should consider when planning a tear-down/cleaning/seal replacement of the said control valves? I I looked at the forums and have read about similar issues, but couldn't find a situation like mine where it wasnt global loss of power. Thanks in advance. Here to learn.
you have all the info there, I just don't know enough about the system to know what it's doing. The key is that one function will restore power to the ones that are weak. Depending on how the system is controlled, it could be different things. Do you have the repair manual for the loader, and what does it say? Do you understand what kind of hydraulic pump and system is on this? Open or closed center to start. That's a little bit of an odd duck, but it is probably similar to another Case, I just don't know if it's similar to a tractor backhoe, or similar to a dozer, or similar to an excavator.
Here is an image that you can find on www.mycnhistore.com . Items 17,18,18a,20 and 21 are the problems. You will have to change the orings on all of them in each section. You will need to use OEM orings no substitutes for these.
Thank you, everyone. I'll order the parts and report back once replaced. I really appreciate everyone's help.
Just for anyone who might be looking at this. Changed the o-rings on the primary and secondary shuttle, which ranged from disintegrated to only partially intact (split or cracked) Pressure in the system went from 1100psi on bucket curl to well over 3500psi. I ended up backing the main relief valve off to spec at 2500psi. Amazing how $30 worth of o-rings can bring a $26k piece of equipment to its knees. Thanks again