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View Full Version : Bobcat Excavator Hydraulic ??


ParkWelding
03-17-2011, 08:04 PM
I'm having a problem with a new-to-me Bobcat 337 mini-excavator (c-series). I was hoping some of you might be able to give some tips on where and how to start troubleshooting the system.

Everything on the machine works excellent with the exception of the right side track drive. That side seems much weaker than the left when going up hills.

When I raise the right track off the ground and step on and release the 2-speed button the track reacts "normally" in reverse. (meaning it spins slower in low, faster in high) When I spin it forward it reacts opposite (slightly slower in high than in low)

Both tracks are tensioned properly, all rollers and idlers move freely, both sprockets have little wear and had been replaced with the tracks approximately 400 hours ago. Final drive oil has been changed in both sides and there was no parts that came out, just black oil.

The only audible clue I have is when the right track slows or stalls while travelling, I hear a slight clicking sound.

I presume that there would be an issue with either the drive motor on that side, or with a hydraulic pump-if each side has its own pump. I haven't bought a manual for the machine yet and will check tomorrow to see if the dealer will print a hydraulic schematic for me. I was hoping that someone on this site might have some insight on this issue. Thanks for reading.

bobcat_ron
03-17-2011, 09:21 PM
Pop some panels out of the floor and look for the linkage cables, 90% of the time they wiggle loose and you loose a bit of function there.

ParkWelding
03-17-2011, 09:46 PM
Ron,

Thanks for the reply. I just had the floor panel and plastic mat out to have a look at that stuff. I had been used to checking the travel/swing/aux pedal pivots in my old BC 325 as they would stiffen up occasionally. On this machine they are all cables, they are all tight and seem to have full travel at the valves.

The clicking noise and the "backward 2-speed" are what had me thinking of a hydraulic issue. Also the symptom seemed to get more noticeable once the machine got hot. Prior to this I had only used it for shorter periods of time, in the colder weather and on a relatively flat paved area. There, and for the first couple minutes I ran the ex this AM the symptom was not noticeable.

Thanks again.

Kepple Services
03-17-2011, 10:01 PM
I had a 435 mini ex, and had the same issue. It is the drive motor itself. Mine self-destructed and had to be replaced.

Giles_uk
03-18-2011, 10:03 AM
have you got a set of pressure gauges check what pressure you are getting to each side, might have a restriction in the flow etc to one side

ParkWelding
03-18-2011, 03:38 PM
I checked the forward pressure line and got 3500psi. Right after that my dealer called and said that the spec as far as he could tell was for 3900psi, but said that my reading wasn't far off and wouldn't cause that problem.

He went through a sequence of testing at the drive motor by measuring the approximate oil output through thru case drain line to determine what the issue is. Will get a fresh bucket of oil and give it a shot.