I have a Bobcat T190 and have recently been having issues with the right track. The machine is about a 2004 (not positive but I can verify the year if needed) with foot controls and about 1,300 hours. Lately the right track does not seem to have as much power. Everything seems to work fine until it has a load applied to it. When going straight ahead and pushing, it will just not move with the lever pushed ahead. The first I noticed it was when I was loading it on a tilt-bed trailer and it was acting almost like it was slipping when I drove it on the trailer. The other day when I was moving bundles of wood, it would act up when I turned to the left using the right track. It would drive, then pause for a second, then drive, then pause and so on, kind of a in a jumpy motion. All other functions are working fine. I have not used the auxiliary hydraulics recently to see how they are working. My dad was using it a few weeks ago with a brush mower and he didn't mention any problems. Is there any way that this could be related? Since we bought the machine new, it has always had a slight whine at full throttle that sounds like it may be from the hydraulic pump. My dad thinks this has gotten a little louder, but I haven't noticed any issues. Not sure if this could be related. The hydraulic fluid, hydraulic filter, case drain filters, and oil in the final drives was changed about 300 hours ago. After researching the issue a little, I read about a charge pressure filter, which I have never seen. I've looked around the machine a fair amount, but I haven't seen anything. Can anyone let me know where this is located? Could this be the culprit? So far I have checked the following: -There are no error codes or warning lights. -I checked the case drain filter for the right track and it was still a bright brass color. If I looked very closely, there were some extremely tiny particles on the filter, but I highly doubt it is any indication of a failed drive. -While I had the case drain filter apart, I checked how much fluid was coming out of the case drain on the right track while the engine was running and it was a very small stream. -I removed the sensor under the hydraulic filter on the back of the machine and hooked up a pressure gauge. The pressure was between 250-275 psi with the engine at mid-throttle. -Should I check this pressure with a load on the hydraulic system? Is there any easy approach to do this? -I removed the hydraulic filter on the back of the machine and there doesn't seem to be any indication of debris in the filter. Thank you in advance, -Ross
Welcome to HEF rpg005. :drinkup It's not likely a charge pressure problem as you don't seem to have any issue with the left drive, problem would be isolated to the right side. A failed drive motor will typically shove metal fragments into the case drain filter for that drive motor. A failed drive pump typically doesn't shove metal fragments into the motor case drain for that pump, maybe some really really fine fragments, that is if the drive motor is in fact good. Debris from a failed drive pump will typically wind up in the main hyd filter at the rear of the machine. Pour the contents of the hyd filter into a clean pan to check for debris. Once you've drained the hyd filter of its oil, pour some diesel in the filter, place your hand over top of it and agitate it, then pour that into a clean pan and see if any large fragments, anything larger than a metal dust, comes out. We also need to eliminate a problem with the pintle arm on the pump control shaft. If that pintle arm gets loose where it clamps to the shaft you'll get jerky operation of that drive, and you typically have difficulty finding neutral if the pintle arm is loose as well as jerky drive operation.
Thanks for the quick response Willie. I will try to check out the filter tonight. When I pulled the filter, I drained it out into a container and was looking for debris, but the fluid looked clean. There was a very small amount of junk at the bottom of the container after I poured out the oil but unfortunately I'm not positive that it was cleaned before I emptied the filter into it. It was mostly black particles (looked like it was just dirt) with a few very tiny pieces that were metallic. My dad needed to use the machine today so if there are any issues, I would guess that the filter would have debris built up again. I've read a little about the pintle arm being an issue. I don't believe that is the issue in this case, but I can certainly check. The reason being is that it just acts low on power regularly without the jumpiness. On every Bobcat track machine that I have used, when pushing hard on something with good traction, the levers will push forward quite a ways without movement from the tracks (and the engine usually bogs down). This is basically how the right track is acting all of the time now, except it isn't bogging down at all. Are there any seals inside the drive motors that can fail and allow fluid to pass through under a load without providing any drive? If so, would the escaping oil come out of the case drain? Is there any way to check the flow from the case drain while putting a load on the drive motor? Would it work to apply the parking brake and move the drive lever? Thanks, Ross
I don't think there's any seals inside the drive motor that would cause excessive case drain flow if they were to fail, but I said I don't think so, can't say for certain, typically motors and pumps don't have seals for the pressure operation of the pump/motor, they're typically components that are precision machined metal to metal interface, and when this precision connection gets corrupted from wear or failure that's when you get excessive case drain flow. A small amount of flow (internal leakage) is normal and by design, this is the flow of lubrication that protects/lubricates the metal to metal interface. I've never done the case drain test as you described by blocking the drive with parking brake and applying drive on that side while checking case drain flow, but I suppose it should work, that's the way you test case drain flow on other final drive motors of other machines. Excessive flow with brake on while applying drive likely indicates motor failure, and I guess you could always do the same test on the left side just for comparison and confirmation.
Last night I pulled the hydraulic filter, drained it, filled it with diesel, drained it, and looked for metal debris. There was some small dirt particles in the filter and a very, very small amount of fine metal particles. I drained the filter into a cup and held a magnet in the oil as I poured it down the side of the cup and there was barely anything on the magnet. I removed the hydraulic oil temperature sensor under the head for the hydraulic oil filter and installed a pressure gauge to check the charge pressure with a load on the track drives. At mid-throttle with no load, the pressure was about 240 psi. I put on the parking brake and pushed the right lever forward and the pressure dropped to about 180 psi. Some of the drop may have been due to the engine bogging down a little. Is this normal? Do you have any other ideas about this? My dad is still fixated on the whine from the hydraulic pump at full throttle and thinks this is the problem. Could this be an indicator of anything? Is there a charge pressure filter on these machines like I had originally asked about, or is that all through the filter in the engine compartment? I looked again the other day and don't see any other filters under the cab. I've just seen pictures like the one attached and it made me wonder.
The filter that you have posted is the filter for the hydraulic operated cooling fan, that's not the main hydraulic filter, that filter is inside the engine compartment. To my knowledge, there is not charge pressure filter as you asked, that's not part of the design. Only a few machines that I'm aware of use a charge pressure filter, JLG machines being one, but I'm not aware of Bobcat doing that. I stated to check the debris in the main hyd filter for clues of wear. If you do find debris in the main hyd filter, dig a little deeper and check the case drain filter for the left side drive. Debris in the main filter tells us there is a problem somewhere in the system. And since we know we have a problem in the left drive, the next step is to check the case drain filter for the left drive and see if metal debris is there, thereby indicating a problem with the left drive motor, especially if the case drain filter for the right drive motor is clean and clear of such debris.
Due to the action of a hot oil shuttle valve for the motors, which I will assume this has, you will normally see a 30-40 psi drop in charge pressure as the valve opens and allows oil to flow out through the motor case drain to the cooler. Any chance this could be something as simple as a stripped spline on a shaft or such like?
Willie - Just to clarify, the right drive is the one that is acting up, not the left. Is it still worth checking the left case drain filter? I was looking around online trying to get a better understanding of how everything works with the hydraulic systems. I've seen people mention about stripped splines or broken shafts before, but which shafts are typically the issue? Are they the shafts/couplers in between the pump sections? Correct me if I'm wrong, but it looks as though the hydraulic pump is driven by the same shaft that comes through the hydrostatic pumps, so if the drives were acting up because of a stripped shaft, the hydraulic pump would be affected as well. Is there a possibility that it is the replenishing/relief valves that are the issue? Is there any way to test these or the pump without elaborate test equipment?
Thanks for correcting me on that. :drinkup Whenever you have a drive problem on a Bobcat one of the first courses of action is to check the case drain filters. Heck, check them both, if the case drain filter for one side is clean and the one for the opposite side is full of debris you can pretty much suspect a failing drive motor. Yes, it can always be a problem with the pump, but motors typically fail more often on a Bobcat than do the drive pumps.
Willie - I will check the other case drain filter this weekend. I tried to before, but that one is plumbed into the bottom of the hydraulic tank, so I need to get a few caps for the lines. I'm also going to check the flow out of the case drains while putting a load on the drive motors. If I have metal in the other case drain filter, I'm assuming it is a pump or motor, but if that one is clean as well, what is my next step?
I checked the other case drain filter and that was clean. With the right case drain disconnected, I started the engine. There was a small stream/steady drip coming out. When I pushed the lever forward with the brake on, it flowed a lot more (not shooting out with lots of pressure, but the stream was the full size of the hose). I tried the same with the left side and it was the same, except when I first started it, the fluid was flowing fast. I moved the lever and there was no change, and when I stopped the track, the fluid slowed to a small stream. I talked to the one service mechanic at the local Bobcat dealer (Best Line Equipment) and he seemed pretty convinced that it was the drive motor. He showed me a parts diagram of a similar Bobcat drive motor and said that it is likely one of the rubber seals failing (there were about 4 large rubber rings in a row). Does anyone have any other thoughts or agree with this?