Bobcat 600 hydraulics (HELP)

MikeHall · Jul 19, 2017

I picked up a 1975 bobcat last week and after getting it running well and inspecting everything I proceeded to do a little work around the yard with it. Yesterday I worked the loader for about 30 minutes digging up and raking roots out of the ground with the teeth on the bucket. Well I parked the loader and went and got some oil and a new oil pressure gauge. I changed the oil, installed the gauge and then went to go do a little more work in the yard until i found that that hydraulics did not work anymore. I have spend 4-5 hours tinkering on this thing and I have yet to figure out what the issue is. I do have some hydraulic movement and it seem the pump is working as I can stall the engine by moving the hydraulics to their limits and holding them. The hydraulics are horribly sporadic moving quick but jumpy at times and then moving ultra slow at other times and even not moving at all without holding a pedal for a solid minute. I was told that the issue sounds like a stuck aux valve but I have wiggled the pedal and looked at the linkage and everything seems to be moving smoothly. Does anyone have experience with these older bobcat loaders?

Here is a video of me working the loader Monday for a bit. I Again everything seemed to work great or at least acceptable as far as hydraulic speed and power.

Thanks
Mike

MikeHall · Jul 19, 2017

I thought I would add that I do have a nice set of manuals that came with the bobcat. Looking at these valves the aux/lift valve does not have the same kind of spool as the tilt valve has. Is it possible even working the pedal of the aux valve the there could be something stuck inside that is not actually attached to the part that moves on the valve? I am not all that familiar with these hydraulics. Here are the parts diagrams out of the manual.

MikeHall · Jul 20, 2017

SOLVED. the issue was just as simple as I thought it had to be. Dang the hours spent trying to figure this out. haha

TUDOR · Jul 20, 2017

Low fluid level?

MikeHall · Jul 20, 2017

Fluid level was the first thing i checked. After hours and hours of tinkering I got in the service manual and just started reading. I came across a part where it mentioned that there was a gauge to tell if the hydraulic filter was clogged up and it worked off vacuum. The thing I had done was unhook that gauge thinking it was an oil pressure gauge. I also determined that the hard line going to that gauge was no longer hooked up to the engine oil as it was bone dry and i could not find where it went into the engine. I assume someone had unhooked it many years ago so all was good to just leave it be. I installed a new oil pressure gauge when i changed the oil in the engine and right after is when i hopped on and the hydraulics no longer worked. That hard line which was now open was sucking in air into the system. It was late last night when i read about that gauge in the manual and I through on some shorts and flip flops and proceeded to hook that gauge back up and instantly hydraulics started working again. It seems there may still be some air in the system as the lift is still a little jumpy.

TUDOR · Jul 20, 2017

:fing32:

CHDinCT · Jul 20, 2017

Was gonna guess air in the system since your issues started right after you changed the fluid. Glad you got it sorted out.

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Bobcat 600 hydraulics (HELP)

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