I have a 2001 Bobcat 773 Turbo with hand controls. Recently the lift arms have been seeping down ~ 6-8 inches immediately after the arms are raised. It will seep 6-8 inches downward and then stop. What's more is that when I roll the left hand control outward to begin raising the arms again and they actually drop until I roll the control out even more and then it will rais the arms... then again as soon as I stop, they seep down another 6 - 8 inches over 5 - 10 seconds and stop. I've thought about the issue being a bad o-ring in the valvebody; however, I would think that the arms would seep down continously. (note: the arms will seep to the gound if left raised.... probaly drop a foot in 30 minutes). I've been told that there is a piston inside the lift cyclinders which go bad and can fluid to bypass which may cause this symptom too. I've also read where the actuators may need to be re-syncronized; however, everything had be working fine and I've been told that they rarely ever need to be re-syncronized... rather the actuators burn up. I hate to start guess at what to try to fix first. Any suggestions and/or ways to prove out any of these theories would be appreciated.
I think the first thing I'd do is take apart the arm lift cylinders and check the piston seals. Your machine does not have holding valves on the cylinders so a bad piston seal can possibly allow the arms to creep down.
one way you could check the cylinders before ripping them apart would be to raise the loader arms in the air and hold it in place by a crane and proper safety support stand, disconnect the hoses for the lift cylinders on both sides and cap the lines and the barrel end of the cylinder fitting leaving the rod end open so you don't create a vacuum....remove the safety stand and let the crane off and see if the cylinders drop...if they drop then there is internal damage to the cylinder ( bad seal, scored barrel, scratched piston, dent in rod)... Good luck
Thanks for the ideas. I ran the machine more today and checked the tempurature of the lift cylinders after everything was warmed up. I had one that was slightly warmer than the other (I figured hot hydralic oil was passing through this one) so I pulled it off and I'm going to have it rebuilt. I hope this is it.
If you had one warmer than the other, that could indicate oil being squeezed by a bad piston seal which would heat the oil. If it were me, I would pull both cylinders, even if the other one has not failed. It's like tires on a vehicle...if the right front tire is bad, the left front can't be far off. You could the failed one now, just to find your doing the other one a month from now.
their are load check valves in the control valve to hold the load while you are moving the lever so you dont get a drop on the load as the oil is flowing through the orrifice its not like a forklift where when you stop moving and shut it off it will stay in that place indefinetly but it is designed to hold the load until there is sufficent oil and pressure to lift it
more than likely though it is in the cylinder though but i have seen the problem in the control valve
I should get the cylinder back on Wednesday and I'll find out if that fixed it. However, if it still does it, I imagine that I'll have to rebuild the valve body. Can new o-rings and such be installed while the valve body is in the machine or do you need to disconnect all of the lines and take the whole assembly into the shop? If so, should a guy just leave the actuators connected and unplug the wires?
it can be done in the machine leave the wires hoked up and sit the actuators where they are supported rem ove the caps slide the spools out reseal reassemble take to the dealer if its a g series to get calibrated
Hi I am new to this and I cannot post my question until I reply to a post 3 times. I apologize in advance for taking up space for someone who can answer your question. I hope this is the way to do this.
after making sure coffee cups pencils and such are cleared from the "red valve" aka lift arm bypass, while it's drifting, lift the seat bar and see if it stops... keeps drifting= bics or cylinder (I'd pull the bics sol. valve and check the o rings on it) stops = problem in the dcv deeper than the bics valve I'd pull any accessible port reliefs - think only 1 or 2 can be accessed in frame, and check them and the o rings on them calibrate the actuators before doing anything
bobcat hand control module my 873 bobcat with hand controls will not lift the boom at times,i have swapped servos and control wiring,the module is bad,1100.00 dollars from bobcat,any reman or after market available ? thanks jim