Low Flow from Aux, No High Flow.

[schemasservice]

Good morning. I have been racking my brain over my 2004 S250 for quite some time. It will run a grapple or other low flow hydraulic cylinder from aux just fine. I get 3100psi at the connectors with a gauge. Problem comes when I'm trying to run a snow blower, or brush cutter. It will spin it up, but when it gets a little load, it slows it down, even stops it sometimes. I have high flow, and pushing the high flow button does nothing. The high flow light comes on, but no difference in hydraulic action. It has been this way for years. I attached the schematic from the service manual. It shows what they are calling a "dump valve ON/OFF" on the pump. The manual has nothing else about this valve listed. Nothing about removing, or testing it. I am assuming this is the high flow valve, and it dumps excess flow when high flow is not engaged. I have no power / actuation of this solenoid when high flow is on or off. Again, I am just assuming thats what this valve is for, as there is nothing else in the schematic for a high flow valve. I can't find any info online, or in Bobcat's wonderful service bible about diagnosing this system. Hoping some one here has some knowledge on this. Thank you. Brian

 

[reaperman]

Just to verify you indeed have high flow? Because the touch pad is standard for every machine even low flow machines.

 

[schemasservice]

Yes, it does have high flow. The high flow button stays lit when pressed, and it has a high flow pump.

 

[[email protected]]

Good morning. I have been racking my brain over my 2004 S250 for quite some time. It will run a grapple or other low flow hydraulic cylinder from aux just fine. I get 3100psi at the connectors with a gauge. Problem comes when I'm trying to run a snow blower, or brush cutter. It will spin it up, but when it gets a little load, it slows it down, even stops it sometimes. I have high flow, and pushing the high flow button does nothing. The high flow light comes on, but no difference in hydraulic action. It has been this way for years. I attached the schematic from the service manual. It shows what they are calling a "dump valve ON/OFF" on the pump. The manual has nothing else about this valve listed. Nothing about removing, or testing it. I am assuming this is the high flow valve, and it dumps excess flow when high flow is not engaged. I have no power / actuation of this solenoid when high flow is on or off. Again, I am just assuming thats what this valve is for, as there is nothing else in the schematic for a high flow valve. I can't find any info online, or in Bobcat's wonderful service bible about diagnosing this system. Hoping some one here has some knowledge on this. Thank you. Brian

Just a thought on this one. I once had a low flow to a digger derrick system and The lead tech could not figure it out or where the issue was. I being an airforce tech, fresh out said It happend under a load? Flow meter and all that used and the flow was low. More when the quick disconnects were put together. I then in passing said check the quick disconnects to see if a blockage happened or one broke. Turned out one of them disintegrated internally and under a load it shut off the flow. Not that it's what you have there but who knows. That dump valve you mentioned we called a deadman in a bucket truck it is designed to dump system pressure if an injury happens. Maybe that is bad or leaks. System relief valve weak and under a load will open also Hard to say without being there to see what takes place. Good luck with all that.

 

[schemasservice]

I don't think it's in the couplers, but that is definitely worth checking. Looking at the schematic, I don't see anything else in it that would control the high flow function. Unless it is controlled through the spool valve in the main control valve? I wish flow meters weren't so damn expensive, or I'd just bite the bullet and buy one. I own an automotive/ light diesel shop, but have never needed one in my line of work.. I already know that my flow is not up to par. But I can dead end the coupler with a pressure gauge and it will bogg the machine with 3k psi. We don't have any good skid steer guys around here, otherwise I'd just take it in.. I can make educated guesses and throw parts at it, I don't want to pay someone else to do that..

 

[[email protected]]

Just a thought on this one. I once had a low flow to a digger derrick system and The lead tech could not figure it out or where the issue was. I being an airforce tech, fresh out said It happend under a load? Flow meter and all that used and the flow was low. More when the quick disconnects were put together. I then in passing said check the quick disconnects to see if a blockage happened or one broke. Turned out one of them disintegrated internally and under a load it shut off the flow. Not that it's what you have there but who knows. That dump valve you mentioned we called a deadman in a bucket truck it is designed to dump system pressure if an injury happens. Maybe that is bad or leaks. System relief valve weak and under a load will open also Hard to say without being there to see what takes place. Good luck with all that.

 

[[email protected]]

I had to go back and read you comment about this high flow valve. Seems the systen runs fine on low flow. And if you push the button for high flow the light comes on. Ok maybe it does but is it shifting the valve to full open or closed whatever it has to change? It sounds like if that valve is not acuating properly the flow is lost or restricted. If you can have someone push that button and watch the valve maybe then you may see the problem. Or can you shift that valve manually? Not sure if that engages a different pump or how they set that up but it points to that valve. Good luck with that.

 

[schemasservice]

I'm sorry, I wasn't clear. The flow issue happens any time the aux hydraulics are engaged. The high flow light comes on, and stays on when the button is pressed, but nothing changes with the attachment. And it does this with both my brush cutter and my snowblower. When the high flow button is pressed, what is actuated in the machine to make the flow increase? I was assuming it was the solenoid on the pump.. Bobcat has that labeled as a "dump valve" in the schematic. Thanks Brian

 

[[email protected]]

I'm sorry, I wasn't clear. The flow issue happens any time the aux hydraulics are engaged. The high flow light comes on, and stays on when the button is pressed, but nothing changes with the attachment. And it does this with both my brush cutter and my snowblower. When the high flow button is pressed, what is actuated in the machine to make the flow increase? I was assuming it was the solenoid on the pump.. Bobcat has that labeled as a "dump valve" in the schematic. Thanks Brian

You were clear what you said. They call it a dump valve. That valve in my mind will dump system pressure. What happens if you don't push that button? Now I am guessing but maybe it releases the pressure you need? Hard to say. Are the auxilary add ons part of the unit or are they just an add on tool? Keep me posted. It is interesting to know the cause.

 

[schemasservice]

Not sure what you mean by auxiliary ad ons being part of the unit? Everything on the machine is factory, as far as I can tell. Snow blower attachment is bobcat brand, brush mower is not.

 

[[email protected]]

Not sure what you mean by auxiliary ad ons being part of the unit? Everything on the machine is factory, as far as I can tell. Snow blower attachment is bobcat brand, brush mower is not.

I wasn't to clear. That's what I was wondering. Compatible Auxiliary ad ons. So that's a wash.

 

[reaperman]

Have you ever saw the machine actually run in high flow mode with the snow blower and brush cutter? Some brush cutters have an inline check valve that doesnt allow reversing the hydraulic direction. Brushcutters are made to run in the counter clockwise direction but running it against the check valve will still allow some fluid to attachment. At work we have a bruchcutter that we need to reverse the hydro direction on the thumb paddle on the right stick. Otherwise, it cuts with the non sharpened side of the blade. We could swap the hydro fittings on the cutters hoses so we didnt have to reverse the direction, but we have a Cat skidder that doesnt reverse the hydro direction. Im not sure how snow blowers work since I've never used one. But both attachments do take alot of hydro flow to operate. The reason I was wondering if your machine is actually high flow is because any standard flow machine is capable of lighting up the high flow light and operate an attachment even in standard mode. Also high flow machines are normally labeled high flow somewhere on the side.

 

[schemasservice]

It does have the high flow label. Not saying that someone before me didn't put that on there as some kind of sick joke. I was under the assumption that non high flow machines would flash the high flow light when the button was pressed, but it wouldn't stay on. That, and the mysterious dump valve that I am questioning shows up in the high flow schematic, but not in the standard flow schematic. That, to me, says it is indeed a high flow machine. I have ran the machine with both attachments in low flow and high flow mode. The brush cutter is not a high flow cutter, so I just did it momentarily to see if it made a difference in performance. The snow blower, is a bobcat brand attachment. I called the dealer to see if it was a high flow snow blower or not. They told me that the machine would automatically turn the high flow off if the snow blower was not a high flow model because they can sense it through the 7way electrical connector. That sounded a little crazy to me, but I couldn't find anyone/ or thing to tell me otherwise.
I have been tolerating this issue for a few years, it is now getting to bother me. The machine runs great and has always been a hell of a work horse... or cat, I guess??? But I plan on bringing it into the shop this fall when I can go without it for a while and tear into this, a long with a bunch of needed maintenance. She's pushing 5k hrs. I've been a master truck/diesel tech for 20+ years, just never got into hydraulic machines and such. I'm trying to take some time to familiarize myself on this before I go balls deep. I found a guy on YouTube (I hear these famous words every day from customers...) but he went into great detail on the hydraulic control valve / system of a bobcat. He explained in painful detail every valve and port on that thing.. But I, for the life of me, can't find anything on this infamous "dump valve", or the high flow system theory and operation in general.

 

[[email protected]]

So what controls the system from High flow to Low flow? Is it that dump valve from what the dealer told you it senses the pressure and may chang from High to low but that is a button that lights up and the system or valve it actuates maybe where your problem is or is it a printed circut that failed and it defaults to Low flow? Just tossing things out there. More ideas the better.

 

[schemasservice]

Ok. I did not know that high flow and standard were 2 complete different deals. I will forget about high flow for now.. I don't really need it, just thought they were interconnected. Lift and tilt work. BUT… I do have an issue with the lift cylinders drifting down. I think that is a control issue. If I lift the bucket and lock the BICS, it stops. And it's more than a "drift". There is power to that downward force, where if I put something under the bucket midway, it will push down hard enough to take a little weight off the front wheels. It won't lift them, but there is definitely downward power. If I counter it with the controls, it stops. Machine has ACS, hand/foot controls. I have recalibrated actuators. Back probing the position sensor at the actuator has exactly 2vDC at the center position. I removed the actuator, nothing looks funky there? Can the actuator be "timed'" wrong? I figured out that the guy I bought it from had been into this thing pretty deep before I got it, so anything is possible… thank you.

 

[schemasservice]

If I lift the lap bar and the BICS locks out, the drift stops. Same thing if I shut the machine off with the bucket in the air, it will sit there all day. I would say that rules out cylinder leakage? And if it's bypassing in the valve, that could also be causing the flow issue with my aux? To throw another piece to this puzzle, my power bobtach is lazy (slow) also. If I run the tilt back till it boggs the machine, the bobtach speeds up. I did read the horror stories about the accessing the bobtach valve, and that if they fail, it's usually a sign that the pump is failing. But this has been going on for close to 1000hrs of machine time. I figured the pump would have completely failed by now if that was the case. I didn't want to throw a pile of problems in my original post, but now it seems like they are all related and trying to tell me something..

 

[[email protected]]

My Old School teachings do nothing to help when if comes to initials like BICS. Or not enough coffee to figure that part out of this massive set of issues. Reading all this only add to the issues but it is hoaning down on the actual problem. That BICS is controling some part of this but what is it that is controls? Safety lock of some kind. Not that familar with that part of this. Actual words help. Thanks

 

[[email protected]]

The Bucket Interlock Control System is a safety feature (not found on most older machines) which "locks" the lift and tilt cylinders to guard against an unintentional bucket movement from an accidental bumping or jostling of the controls. Not just skid steers. Pretty much ALL heavy equipment. On most modern machines this is the "lap bar" that you have to pull down in front of you after you're in the seat. Nothing will move until the lap bar is in position. NOTHING. Everything is electrical now days, so the mechanism is nothing more than a switch which sends a signal to the computer (or to a solenoid on pre-computer machines) to release the lock valve and put the hydraulic system in "ready to work" state. Same concept as the seat switch on a lawn tractor. Nothing works until you sit in the seat.
I love my 720. No seat switch, no "BICS", no lap bar, no computer. Old School all the way

Hey thanks for your explaination. I also rather have the OLD School method and let the operator think more about what he or she is doing.
Dirt, and electric swithes do fail. Have a good labor day weekend.