my 331 bobcat lost all hydraulics. I've checked pump connector, fuses and now I'm looking for the solenoid that is operated by the console safety switch. It is so tight by the solenoids it's hard to unplug and check, but if I know which one exactly I will work at it I'm a new member and need help. any help would be appreciated. there is five solenoids all color coded with tie straps but which one?
bobcat lost all hydraulics on 331 mini excavator
- Thread starter crazy man
- Start date
SSdoxie
Elite Member
If you lost all hydraulics including blade and travel and still has fluid in reservoir, the only the most likely failure is nylon gear disc that bolts into the fly. This drives the steel gear on the pump shaft.
I pulled pump off and gear on pump was fine and gear on flywheel looked ok but I only looked at front half of the gear. should have inspected it better. will pull it off again and try to see rear half, or feel if any cogs are broken thank you
SSdoxie
Elite Member
Possibility that the pump gear has loosened on shaft and moved forward so teeth are only engaging a portion of the nylon tooth width.
What is the serial number of this 331? The 331 covered several years of production had several design changes during production. One of major changes was introduced when 331D came out, the D series and later use a variable displacement, load sense pump. Earlier versions had 3 section gear pump. All versions used mechanical linkage on blade control, meaning that the are rest switch did not affect this function so diagnose problem using the blade function.
Now if it is a D series or later, has piston pump, and drive coupler is fine and no blade function, that narrows it down to problem in load sense circuit. When engine running with all functions in neutral position the pump is at minimal stoke moving just enough fluid to maintain the pilot pressure at the joystick. When any valve is activated the change is pressure and flow is sensed through the load sense line from valve to pump allowing the pump to move to on stoke sending fluid to the function.
Summary: If all functions are inop including blade and machine has a gear pump only commonality to all functions is the coupler. If it has the the piston pump the pump coupler or load sense circuit could be the issue.
What is the serial number of this 331? The 331 covered several years of production had several design changes during production. One of major changes was introduced when 331D came out, the D series and later use a variable displacement, load sense pump. Earlier versions had 3 section gear pump. All versions used mechanical linkage on blade control, meaning that the are rest switch did not affect this function so diagnose problem using the blade function.
Now if it is a D series or later, has piston pump, and drive coupler is fine and no blade function, that narrows it down to problem in load sense circuit. When engine running with all functions in neutral position the pump is at minimal stoke moving just enough fluid to maintain the pilot pressure at the joystick. When any valve is activated the change is pressure and flow is sensed through the load sense line from valve to pump allowing the pump to move to on stoke sending fluid to the function.
Summary: If all functions are inop including blade and machine has a gear pump only commonality to all functions is the coupler. If it has the the piston pump the pump coupler or load sense circuit could be the issue.
the serial # is 232511174 will check coupler again. you are right no blade function or travel, the thing is stuck in my driveway thanks for your input! it is a D series
thanks for all the time you spent on trying to help me SSdoxie! it turned out to be console safety switch. thanks again
SSdoxie
Elite Member
Glad you got it going. This is first time in 18+ years of Bobcat dealer troubleshooting assistance that I heard of arm bar (pilot pressure lock out) affecting a mechanical controlled valve (blade).
Go figure! I was at a loss of what to do. the only reason I knew about the switch was I replaced the five or six hydraulic hoses in left console and seen switch. took chance that was my problem,and ordered the switch. then I did some research and joined tractorbynet ,got some good info and proceeded to pull pump and check that. anyhow when I got the switch and unplugged old one it broke in half! I'm not a mechanic but a welder, not real good at diagnosing but ok at wrenching the worst thing was it was stuck in my driveway this is a 2001 hope you are around when I have my next problem thanks again
Just parked my 331 for a month and now I have no hydraulics checked oil filled no obvious damage wondering if it maybe a electrical switch somewhere stopping the hydraulics working
my 331D had no hydraulics at all,no blade nothing. pulled pump, gear fine. turned out to be magnet sensor in left console. I think part # is 6675665. I think it was about 50-60 bucks. if I remember right the sensor cracked and you could visibly see it after looking closely good luck