I've been using my 843 like crazy with all the snow we've had. I've noticed that my lift arm hydraulics seem a little spongy. When I'm trying to scrape down to clean pavement- I tilt the bucket forward -lifting the front wheels slightly so the edge really bites down. But- as I encounter varying resistance- the whole machine tilts fore and aft (front tires get higher and lower) because my lift arm rams are moving slightly - like there is a cussion of air in the cylinder. I know oil doesn't compress and all the pivot points are tight so I'm trying understand if some movement is normal (from hose flex) and if so- how much? Also- if this is not normal, is there any way to fix this?
I wouldnt call it normal but I have seen it before especially when the unit is not operated through a full cycle of the rams. The oil may be foaming as well causing some of the give. Run the rams through the full range of motion a couple of times when you notice the give and that should help. You may have some piston seals that are leaking a little letting the oil foam. It does happen just make sure the oil is up to spec and keep an eye to make sure something else isnt developing.
Thanks frogfarmer but I've already done that. I'll do it again just to be sure. When i got the machine, the wheel motors were unhooked so the machine could be rolled (engine was dead). When I rebuilt it, I replaced all filters, added new fluid and cycled everything to the full extents. Maybe there's some air in the oil?
May be a long shot, but are you certain the loader arms are not set in float position? When "float" is selected, and you tilt the bucket forward, it will typically raise the machine a bit, then the loader arms with float up and allow the machine to tip back foward.
pardon my ignorance, but how would I know if "float" is selected? The machine is pretty new to me and while I have all the service manuals, I've not been able to source and owners manual. I don't think the arms are floating because they seem to always return to the set position... it's just that they "bounce" a little based on load. I would say the pistons on each arm moves about 1/2-3/4 of an inch (load dependant) almost like there's air in the oil but I can't fathom that with all the cycling I've been doing stacking snow up high that there would still be air. I did fill up with genuine bobcat hydraulic fluid when I replaced all the hydraulic filters but- my auxiliary hydraulic connectors were not sealing well at all. I ended up replacing them and topped off the tank with generic 32 weight Hydraulic oil. I can't imagine that would be the source? Lastly- my machine did not have the hydraulic sensor/switch under the seat... it only has the sensor on the large hydraulic filter in the engine bay. In looking at the manuals, it seems the previous owner removed the under seat sensors and I can't really tell where a new one would even go. Unfortunatly, I don't know of another 843 to get a look at that sensor. I don't know if a fitting was removed or if the port is plugged and I just don't see it. I never really worried about this because the hydraulics are so strong. The Hydraulics light has always been on but I figured this was because of the missing sensors. now I'm wondering if this issue is related? Any guidance is appreciated and I'm eager to learn.
Ok, if it's just moving 1/2 to 3/4", doesn't sound like you have float engaged. May be time to do a simple check of the piston seals in the arm lift cylinders, but you're gonna need a #8 JIC plug fitting to do it, and you're going to spill a little bit of oil from the cylinder you're testing. Lower the loader arms all the way down, shut off engine. Disconnect the lift hose of the right lift cylinder. This would be the hose connection for the rear of the cylinder. The retract hose connects to a long tube that goes down the length of the cylinder, don't disconnect that one. Put a #8 JIC male plug fitting in the disconnected hose to block it off. Start engine, engage hydraulics. I'm thinking loader arms are controlled by the left pedal. Push the pedal forward to gently load engine with hydraulic load, put a pretty good load on it, monitor the disconnected fitting on the cylinder. If it starts leaking oil, you have a bad piston seal. Perform same test on cylinder on opposite side. BTW, loader arm float is done by pushing pedal all the way forward until it clicks into a detent and the pedal holds down in the far forward position. In this postion, the arms will float up and down as you're back dragging. Also, if the 843 is anything like the 743, be careful having the engine running and not being in the operator seat. The 743 was notorious for creeping. And check the pin boss where the bucket tilt cylinder pins off to the loader arm frame in the center. That pin boss is bad about cracking either the weld or the steel at the edge of the pin boss weld. And, welcome to the forum jav.
Thanks so much! I understand the instructions and will try it when I get a chance. Yes- the 843 also has a tendance to creep but VERY VERY slowly and the parking brake seems to hold it (at least mine does). My machine seems to have been lightly used. The pin boss on mine is pristine- never even repaired. The only real "issues" I've had with the machine after the rebuild has been solving the Hyd. light issue, this sponginess in the lift arms and I know my tilt cylinder rod needs work -it's pitted and the the seal leaks a little. Other than that, and dispite these issues, the machine is a little beast! I don't know what I would have done without it this year.