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T190 Right side track problems

Discussion in 'Skid Steers' started by NCPIPELINE, Feb 7, 2014.

  1. NCPIPELINE

    NCPIPELINE Senior Member

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    Had replaced this drive motor last year when I found metal in case drain filter, guess I am going to be opening that side up again today. It does respond just very sluggish, sometimes not at all. Anyone ever seen this problem? It has on occasion thrown a code for charge pressure? :pointhead
     
  2. NCPIPELINE

    NCPIPELINE Senior Member

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    Lets add a little bit more to this now, same sluggishness in ISO or H, checked case drain looks good, nothing abnormal. Both hydraulic filters are new.
     
  3. NCPIPELINE

    NCPIPELINE Senior Member

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    Put the machine is H pattern so I could directly control the right side track (that's where my problem is), after I get it nice and warmed up it starts to act up with trying to use the right track to turn left or right or simply to back up. It almost feels like the brake is engaging on that side, ideas?
     
  4. NCPIPELINE

    NCPIPELINE Senior Member

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    Talking to myself again LOL! Questions: when the brake comes on, does it applied to both sides from the same "valve" or are there separate valves for each drive motor brake? I was watching the charge pressure, when the right track started to not respond the charge pressure had fallen from 300 or so down to 140, but as soon as I stopped trying to operate the right side track the charge pressure came right back up.
     
  5. willie59

    willie59 Administrator

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    Both left and right drive motor brakes get pressure to release from the same port on the brake valve, not two separate valves. It sounds to me like the rotating group is going down for the right drive pump, that would explain your loss of drive power for that side and the loss of charge pressure until you let off the right side, then charge pressure recovers.
     
  6. NCPIPELINE

    NCPIPELINE Senior Member

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    Willie, just to clarify is that the drive motor or pump?
     
  7. mikebramel

    mikebramel Senior Member

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    Both, in a closed loop both components are dissasembled and inspected when one fails. Otherwise the old will cause the new to fail
     
  8. willie59

    willie59 Administrator

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    What we do know is the right side drive motor went down and you replaced it. Like Mike stated, the proper procedure after a motor failure is to flush the system, the most thorough would be disassembly of all components, drive motors and drive pumps, to remove any debris from failed motor. In many cases this is either not practical or is cost prohibitive to the user so they opt for simply replacing failed motor. The danger can be the debris generated by the failed motor can damage or destroy the rotating group of the pump that drives that motor. It's a roll of dice, no way to predict if it will destroy the pump or not, but it can happen.

    Here's a simplified diagram of how your system works. The reservoir feeds oil to the implement pump (8). Oil leaves the implement pump (red line) and goes to the loader control valve. Assume you're not working any loader functions, then oil goes straight through the control valve.

    Oil leaves the loader control valve and becomes the charge circuit (orange lines). Prior to getting to the hyd filter, the brake circuit (green lines) Tee's off of the charge line to operate the brake circuit.

    The charge circuit goes through the filter, then goes to charge (feed) the drive pumps with oil. Pressure on the charge circuit is maintained at 245-255 psi by the charge pressure regulating valve (6).

    Charge pressure feeds oil to the drive circuit/s (purple lines). The drive circuits are closed loop, from pump to motor, back to pump, back to motor, etc, the charge circuit simply keeps the drive circuit/s filled with oil as it's lost, either by case drain leakage, popping open a drive relief valve, or oil loss by operation of the drive flushing valves.

    Oil lost by leakage at the drive pumps go through the pump case drain lines (blue lines) and goes right back to the implement pump to travel back through the circuits.



    Bobcat T190 drive circuit diagram.jpg



    A key symptom is the loss of charge pressure when operating the right drive. You don't loose charge pressure when using the left drive, only the right. This eliminates a problem with the pressure regulating valve as well as a problem with the brake circuit, it indicates you have a problem only with the right side drive circuit.

    Could it be the motor failing? Not likely, if the motor failed and had excessive case drain leakage it wouldn't necessarily make charge pressure drop. And even if it did have catastrophic failure that made charge pressure drop, it would struggle to drive at all on that side. And you'd also notice other symptoms with drive problem on that side, noises, something you feel in the drive, maybe things you noticed last time that drive motor went down.

    What can happen to cause charge pressure to drop as you describe. If you have a bad rotating group on a pump, you get excessive leakage between mating surface of piston housing and valve plate. It may push enough oil to work a motor under a light load, but under hard working load demand, the leakage at drive plate is too great. You now have oil hemorrhaging at the drive pump, oil is dumping out the case drain of pump. Since oil is being lost at this rate, the charge circuit is attempting to keep circuit filled, but the oil loss is greater than what the charge circuit can supply so charge pressure drops, until you let go of the right side drive, pump recovers (somewhat), charge pressure stabilizes. Of course there's no way I can say with 100% accuracy that this is your problem, only suggesting that the symptoms indicate this is your problem.

    I hope this all makes sense. :)
     
    Last edited: Feb 10, 2014
  9. NCPIPELINE

    NCPIPELINE Senior Member

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    YOWSER! Thanks guys. It does make sense to a degree. What is the corrective action? Is it replacing just the bad section in the pump or a new pump?
     
  10. NCPIPELINE

    NCPIPELINE Senior Member

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    Anyone have a write up or can lead me in the right direction for pump replacement? As you said drive motor not likely, leaning towards pump at this time.
     
  11. willie59

    willie59 Administrator

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    You could either have the pump rebuilt by a competent shop or go for a reman. Loader Parts Source is a good source, a bit cheaper than Bobcat. You might consider doing a stall test on the pump just to verify. This would involve checking flow and pressure, but not everybody has access to a flow meter. You might glean some info by simply checking pressure by disconnecting a drive hose from each side (one side at a time), plug disconnected hose, and connect a pressure gauge to the port on the pump. Have parking brake on, good bit of throttle, slowly engage drive that the gauge is connected to and monitor pressure, see at what psi it drops off. If right drive pump has substantially less stall pressure than left side, likely a failed pump.
     
  12. NCPIPELINE

    NCPIPELINE Senior Member

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    Willie sent you a message
     
  13. NCPIPELINE

    NCPIPELINE Senior Member

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  14. willie59

    willie59 Administrator

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    Oh, didn't know your machine has selectable joysticks. I haven't worked on one of those pumps, Loader parts source should be able to confirm if it's the correct replacement pump. As far as testing the pump, if it has a failed rotating group, a stall test should show this. I have access to a flow meter with a pressure gauge to do such tests, but I realize you may not have such a tool, so I'm thinking a simple pressure test will give some useful info.

    It's actually quite simple. There's four hose connections to the drive pump that go to the drive motors. The two fittings indicated by red arrow are for the right side drive, the two fittings indicated by the green arrow are left side drive. Disconnect the top hose for the right side, install a JIC plug in the hose fitting. Install an adapter on the fitting on pump to connect a pressure gauge, any hose shop should be able to provide a female #12 JIC to pipe thread adapter to connect a gauge hose.



    Bobcat T190 drive pump hose connections.png



    Start engine, engage parking brake, depress the enable button to enable drive, throttle engine up, the slowly move drive lever for right drive. Monitor increase in pressure until it reaches the point that pressure either no longer increases or decreases rapidly, note that pressure.

    Remove pressure test and move it to the top fitting for the left side, perform same test. If the stall pressure for right pump is considerably lower than the left pump, fault in pump. The pressure relief for both drive pumps is 5000 psi, and you should see that pressure on your gauge so be sure you're using a gauge and test hose that can handle that pressure.
     
  15. NCPIPELINE

    NCPIPELINE Senior Member

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  16. willie59

    willie59 Administrator

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    That's what I use, liquid filled gauge with stainless steel case. 7500 psi should be sufficient.
     
  17. NCPIPELINE

    NCPIPELINE Senior Member

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    Cool, I ordered it and have a hose and plugs ready. So I guess we will go from there. Working on replacing the tilt actuator on the A300, wondering if for sure will need to calibrate? It is a keyed machine. Does it have to be done via bobcat computer?
     
  18. willie59

    willie59 Administrator

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    I haven't had to deal with those controllers yet, don't know what's involved in repairs and calibration. :)
     
  19. NCPIPELINE

    NCPIPELINE Senior Member

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    I replaced the actuator with no problems, code went from 38-12 to 38-40, LOL! Guessing maybe it has something to do with calibration since the code is for tilt actuator short to ground.
     
  20. NCPIPELINE

    NCPIPELINE Senior Member

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    How long would you make hose to gauge?