Bobcat T190 drive problem

[Potterx]

Guys, new to bobcats and have an issue with my T190.

Here is background, purchased a 2003 T190 with 3400 hours on it. Changed fluids and did simple services to the unit as soon as we got it. Ran the unit for 150 hours or so moving dirt and clearing timber. From the beginning the unit seemed to be sluggish when going uphill (seemed to stall out with levers full forward, back off and start again)but on flat ground seemed to work well(although I have never driven or owned a tracked unit). Also in mud the left drive would not spin out.

While moving a lot of dirt the left drive seemed to start to feel like it had loss of movement to where I started to modify my driving to compensate and use the right side in reverse to turn right instead of driving forward with the left. It feels like surging almost, like it moves fluid then stops then moves fluid again. You have to move the left joystick a few inches before it seems to engage the drive as well.

Based off what I researched and I found videos describing how to check the drive motors by looking at the case drain leak by. I completed the leak test and found that both drives had "excessive" leakage( full hose flow), but the left drive appeared to be more. Also during this process and when I first purchased the unit I checked the case drains for each drive but no real material/ debris in the screens.

At this time my assumption was that the drive motors were my problem so I purchased 2 rebuilt drives from Final Drive Parts and installed them. Once I started it up and driving it i could tell that the drives did not stall out going up the hills but the left drive still was "surging" and "delay" in joystick on the left drive.

Based off above I assume I have a drive pump issue, so I ran tests by placing gauges on charge and then each drive. At idle the charge pressure is 80-100 psi, and at full RPM 160 psi. Right side pump discharge it maintained 160 psi charge pressure and the drive pump pressure I got up to 4000 psi and ran out of my gauge. Left drive maintained 160 psi charge pressure until the "delay" in the joystick then it jumped to about 220 psi but then dropped back to 160 psi. I then continued to load the pump up until 4000 psi as well. I could repeat the process every time.

I am unsure why the pressure jumps when the left pump actually engages.

At this point I think my drive motors and drive pumps are in good conditions? Thoughts? I am not sure why the left drive does not move the unit though. I am unsure what this "delay" or loss of movement is.

Is there a relief valve somewhere that can only affect the right side, am I missing something?

Thanks

 

[willie59]

Does your machine have Standard Controls, Advanced Hand Controls (AHC), or Selectable Joystick Controls (SJC)

 

[Potterx]

It drives with levers, but has selectable bucket/boom controls either joystick left/right or foot pedals, is that considered SJC?

 

[willie59]

Drive levers look like this?

 

[Potterx]

Yes it does

 

[willie59]

Ok, that's the Advanced Control System (ACS), what I called Advanced Hand Controls previously, I gotta quit doing that, it's ACS.

I'm not sure what your problem is at this point as I've never experienced your problem before. However, the charge pressure you reported seems a bit low. All the T190 diagrams I've looked at the charge pressure is somewhere between 220 and 270 PSI, roughly.

Where did you tap into the system to check the charge pressure?

 

[Potterx]

I removed the charge pressure sensor on the left(driver) side of the hydraulic filter. Installed a fitting then tee with sensor and pressure gauge installed with a hose into cab. I do get a charge pressure alarm at times, before checking pressure with gauge I thought maybe the sensor was going bad( had that happen on engine oil)

 

[willie59]

Well, that's where Bobcat says to tap in to check charge pressure. Again, I don't know if that's what's causing your problem, but that charge pressure seems a bit low for the specs Bobcat calls for.

Are you getting any fault codes?

What about loader functions, any problems with loader not able to lift a load or such?

 

[Potterx]

I figured it was low based off your comments from other posts,but it seems to be enough to provide fluid to the drive pumps so was not sure what minimum was.

No fault codes that I am aware of, I will check again though.

No real issues with loader, it slowly drifts down when raised up, assume bad seal. Aux hydraulics running a brush hog and driving the unit causes the brush hog to slow down a lot and not work well. Starves the aux hydraulics. This was all before I replaced the drive motors, and assumed it was due to the excessive leakage through the case drains. I have not tried using the hog since, will try to hook it up this weekend and see how it operates. We also figure we had to large of a drive pump on the hog, so we got a smaller one and installed. Thought I had high flow, but guess not.

A test I thought about doing was buy some extra fittings and a few elbows and flip the 2 top drive pump discharges( Hook right to left, and left to right on the hoses). See if it acts the same. Should give me a second check on dive motors and hoses if the problem switches sides when hoses are flipped.

 

[partsandservice]

I am not familiar with this application, that being said. I would think each loop, left and right should have separate charge pumps. So charge pressure should be measured in two spots. Also both pump and motor in the loop should be addressed together.

 

[willie59]

I figured it was low based off your comments from other posts,but it seems to be enough to provide fluid to the drive pumps so was not sure what minimum was.

No fault codes that I am aware of, I will check again though.

No real issues with loader, it slowly drifts down when raised up, assume bad seal. Aux hydraulics running a brush hog and driving the unit causes the brush hog to slow down a lot and not work well. Starves the aux hydraulics. This was all before I replaced the drive motors, and assumed it was due to the excessive leakage through the case drains. I have not tried using the hog since, will try to hook it up this weekend and see how it operates. We also figure we had to large of a drive pump on the hog, so we got a smaller one and installed. Thought I had high flow, but guess not.

A test I thought about doing was buy some extra fittings and a few elbows and flip the 2 top drive pump discharges( Hook right to left, and left to right on the hoses). See if it acts the same. Should give me a second check on dive motors and hoses if the problem switches sides when hoses are flipped.

"Seems to be enough" is dangerous thinking when it comes to the charge pressure on hydrostat pumps. Again, I've never seen your problem so I don't know what the cause and effect would be, but Bobcat specs between 220 and 270 psi for charge pressure, far more than what you've posted.

As for fault codes, going back to your original post (being new to Bobcat machines), are you aware that Bobcat machines don't "store" trouble codes? Bobcat's only work with "active" codes, faults that happen real time, when you shut the machine down everything resets. The key to Bobcat machines is the alarm. When you turn on the ignition to power up the machine you should hear a single/long beep from the alarm. This is the ECU doing the self test and also lets you know the alarm is working. During operation of the machine, if you ever hear the alarm make 3 short beeps, that's a fault that the ECU is seeing. Right then, the moment you hear those three beeps, push and hold down the headlight button, this will bring up the "active" fault that caused the beeps.

As for swapping the drive pump outputs, you can't swap just two, the two "upper" connections, you have to swap all four connections to the drive pumps. If you do that it could yield some useful information.

And I'm still not sure of your symptoms and your problem, but just for the helluva it, are you certain the drive belt has the proper tension?

 

[crewchief888]

I am not familiar with this application, that being said. I would think each loop, left and right should have separate charge pumps. So charge pressure should be measured in two spots. Also both pump and motor in the loop should be addressed together.

bobcat uses a single charge pump.

:drinkup

 

[Potterx]

Tried test again tonight with oil cold, charge pressure slightly higher, when left joystick is released charge pressure still jumps up to around 220, then drops back off to 180-200 .

I have learned about the bobcat faults, none currently.

Belt is tight, 3 o'clock position on indicator. Loosened, moved set it back up, same location.

 

[Potterx]

Another test completed:

With bobcat jacked up and on blocks monitoring charge pressure.

At low idle RPM:
Right drive 100 psi, when engaged(driving/lever full forward)100 psi charge pressure.
Left drive 100 psi, when engaged(1/2 way through stroke when drive engages up to full stroke) 200 psi charge pressure.

At full throttle( holding opposite lever(drive) in neutral)
Right drive 200 psi, when engaged 200 psi
Left drive 200 psi, when engaged(like above) 280/300 psi charge pressure maintaining.

Also when engaging right drive if you don't hold left drive in neutral(keeping constant tension), the left drive slightly engages(think this is normal?) and causes the "surging" making charge pressure bump from 200 psi to 280 on each surge.

Any ideas?

I am getting some short jumper hoses made up to swap left to right, and right to left supply hoses to drives. Let you know if the left drive maintains the issue or it transfers to the right drive.

Thanks

 

[Potterx]

Okay, got a few hoses to flip sides. There is not a lot of room to change both sides at the same time, so I did one side at a time and capped off the other, with the skidsteer sitting on blocks.

My issue did switch to the other side.

When I hooked the left drive to the right drive pump it operated properly with no issue. Full throttle charge pressure 200 psi, when drive engaged maintain 200 psi.

When right drive hooked to left drive pump, delay in engagement like before( roughly 2-3" in stroke before drive moves), at full throttle, charge pressure is 200 psi and when engaged jumps to 280 psi.

At this time I am at a loss. The only thing I can figure is maybe the left drive pump is good enough to maintain proper discharge pressure but not enough oil flow to give enough torque to move the skidsteer at normal speed. Things I can't explain is why does the left drive pump causes charge pressure to increase to 280 psi, and why is there this 3" drive delay engagement on the joystick.

I am wondering if my next step would be to get the skidsteer to a dealer and see if they can complete a flow test to verify pump output.

Thoughts?

 

[partsandservice]

It seems as though you have isolated it to the left drive pump. Flow and pressure are two things. A dealer ship flow test would be a waste of time IMO. You started with excessive case drain on the left drive motor. That failure most likely caused the damage to the left pump. They should be addressed in pairs. Do the left and right pump share a common case drain? If not a case drain test of the left motor would be in order.

 

[crewchief888]

remove and check your filters, including the case drain filter(s) for debris.
brass is most likely from the pumps, metallic debris is most likely from the drive motor

:drinkup

 

[Potterx]

When this issue first showed up, I assumed that the left drive motor failed, so I performed a case drain test(this unit has 1 filter for each side). I saw what was described as "excessive leakage" by viewing videos online by final drive parts. I then decided to go ahead and replace both drives since the unit had 3500 hours and this was described as one of the biggest issues. I then pulled case drains and inspected. No real pluggage or build up, no brass, no metal. Installed rebuilt drives and verified leakage to be good and within spec. Buttoned things up then took the unit out to try it out. All and all I could tell an increase in overall torque and stronger due to the drives being replaced, but the left drive still was not correct. It seems to have roughly 1/4 the power the right does.

I think when I purchased the unit it had out of spec leakage in the case drains but it operated good to my knowledge, it was the loss of drive power on the left side that got me looking. I don't know that the left drive I replaced got any worse then it was when this loss of power happened. I might have wasted money, but now have good drives that are known( since it acts the same as it did after drives were replaced)

Unless there is a something in line I am missing almost has to be the pump, but it is able to reach high pressure.

 

[mikebramel]

The problem is you have 25% power on one side in relation to the other. If the left side had a failure ruining the old motor, that same debris will have damaged your new motor. In a closed loop, or hydrostatic circuit, the oil flows from the pump -> motor -> back to the pump. Any failure is exponential. If you were lucky you would have a stuck flushing valve..... But I don't think so. You should have taken the money you spend on the right side motor and put it into the left side pump. But, I understand you are probably a bit hesitant to take the whole stack out. A lot of hydraulic shops are crooked and will charger $1500 to reseal.

 

[Potterx]

Where is this flushing valve located so I can check it out before I go and pull the pumps? Will it effect only one side, and not the other?

As far as pulling the pumps, is it possible to pull the pumps out throughout the front of the unit? Or do you need to pull pumps and engine together? When pulled for the money my best bet is to get a reman pump assembly and install, vs having a shop just fix the left drive pump I assume. I don't see to many shops on the Internet, who would you suggest? Looks like loader parts source is the guy.

Thanks