Hi all, So i bought a used Cat skid steer recently and bought a new grapple for it the other day. Machine has about 3800 hours but has new engine and new hydraulic system that was flushed and installed approx. 400 hours ago. The grapple claws will open and close but leak down when at rest in up position and will lose pressure when biting down on material. I've done all the necessary easy DIY troubleshooting that i know of. Grapple cylinders aren't bypassing, all grapple hoses are leak/debris free, quick connects have been changed on grapple and machine arm. No visible leaks of any kind anywhere. When claws are at rest in up position i can hop out and disconnect the male end line on the arm and they stop leaking down. When they leak down from full up position it takes about 55 seconds for them to close, first the left claw, then the right. This makes me think its a valve stuck open on the machine side. A mechanic told me it could be a spool valve? I've searched Cat diagram parts and there's no spool valve that i can find, is it a different name for this machine? I found a valve body that has multiple valves and solenoids would that be the spool valve he's referring to? Would this mechanic be on the right track to diagnosing what's going on? Mechanic is former CAT certified mechanic so I'd assume he knows what he's talking about. Any info on experience related to this issue would be greatly appreciated. Thanks.
AFAIK there are no spool valves on a 299DXHP so draw your own conclusions about what you've been told so far.. Post a Serial Number to confirm. JSTxxxxx I imagine.? Does this look somewhat like the valve body you are referring to.?
SN# DX202385. Yes, the diagram you've posted is the valve body that I've seen. I would assume this is the only other location that would have a valve for the A2 hydraulic supply.
The two proportional solenoid valves for the AUX function are circled. Inside they look like the photo on the right, not a spool in sight. I would have suggested that you swap them but if you say that the grapple cylinders bleed down in both directions it's hardly worth it. Switching tacks - post a photo of the dash panel in the upper RH corner of the cab please. Let's see if you have onboard access to electronic diagnostics.
this is the dash i have, disregard the machine code, that code has been resolved.
Excellent. You have the Advanced Display. Use the Menu Entry icon (#40) to help you get into the "Status Parameters" sub-menu where it shows the inputs from the joysticks and thumbwheel roller (I'm assuming that you use the roller to control your AUX). It will be interesting to see what output there is from the roller when it is in the centre position. All these controls have a PWM output and should register 50% duty cycle when the joystick/thumbwheel roller is in the centre position.
It does have the thumbwheel roller. This is what i have at idle. No status for the thumbwheel roller.
TBH you didn't even need the motor running. Simply turning the key to the ON position would have produced the same results. What happens if you move a joystick from neutral (centre) fully in one direction then fully in the other direction.? That is unfortunate. In that case you're going to need Cat ET hooked up to the machine in order to monitor the position of the thumbwheel as it is rolled back and forwards. What I'm trying to get at is whether the movement of the cylinders with the thumbwheel in the centre neutral position is anything to related with signals that the Machine ECM is receiving from the roller switch. If it is proved that the roller is not the culprit then the process moves on to check whether or not any output is going from the ECM to the AUX solenoids.
When i move the sticks it reads the percentage of movement on each axis. When i release they go back to zero. I understand what you're saying. Maybe the tech I've been using has this software or at least the basic version of it. If not I'm sure somebody around my area may have it. But I can pass this info along, or at the very least, act like i know what i may be talking about.
There is a possibility that you know more than they do at this point........ It's jumping around a bit but maybe you could try a clamp-on ammeter on the wires to the AUX solenoids on the main control valve (see Post #4 above) and with the engine idling see if there is any power going to either of those solenoids. That might achieve the same objective to either confirm/deny any input to the solenoids from the machine controls.
I can check. I should have some results posted tomorrow around this same time as i am no where near my tools at the moment. Feel free to check back in tomorrow. And thank you.
Reading this I wonder if there is a possibility that some contamination that the flushing process missed is affecting the operation of the proportional solenoids for the AUX function. It probably wouldn't hurt to pull them out and check. Just be careful not to damage the 3 x O-Rings on each valve because I don't see any separate Part Numbers for them.
I will check that too. Ive got a wealth of seals and o-rings related to the hydraulic system so i may have them. But then again. Maybe i dont want to poke the bear and just let the tech do it.
My apologies for not getting back sooner, we've been dealing with a bit of weather here in Florida and other areas. My heart goes out to the entire Southeast US, especially ones affected in North Carolina, Virginia and Tennessee where this storm has washed away whole towns in some cases and has cut areas affected there off from the outside world pretty much. Issue has been located. I broke down and finally called in my mechanic. First things first. Check my original post and note that i did the proper diagnosing on the grapple cylinders and quick connects and checked for visual leaks everywhere before moving onto the hydraulic system under the cab. Determined to be this Flow Control Pump valve that attaches to the bottom of the hydraulic pump. One of the shafts inside is in a bind, almost as if seized in place while the other moves fairly easy and then springs back into place. My understanding is trash somehow got in there and either seized the shaft or possibly warped the shaft. Either way, tapping with a narrow punch and small hammer wont budge it and it is stuck in a position where it would allow fluid to bypass back through that valve. Not hard to get to, not an expensive fix compared to other hydraulic system failure's. But i wanted to come back and report my findings in hopes that it will help the community with diagnosing their own equipment. View attachment IMG_8885.jpg
Contamination can be a bigger to deal with, even after the supposed “cleanup” has been completed….
Ugh....so disregard what i thought was a victory. Installed new pump control valve, grapple claws still continue to leak downward. Checked parameters with Cat ET software as it pertains to thumb roller position, no leads there. Checked the electrical and signal inputs for proportional solenoid valves for the auxiliary functions, nothing out of sorts there. Pulled out the two solenoids and checked them for damage/debris and nothing, looked clean on the screens. We're at another loss, time to do more research. I'll add that the grapple claws leak down in the same amount of time as before, so nothing we've done has even slowed it down or sped the process up in anyway.
I'm thinking that the issue, wherever it is, is related to the contamination you referred to in your original post.
Are you sure that both sides are leaking down? This is what's going on in the aux valve section. There are a couple of possible leak paths with the valve in neutral. The shutoff valve (34) is a possible leak path for one side. The line relief (21) or the check valve above it could affect the other side. I don't see anything that could affect both sides except the the main spool.
Let me back up. When i say both leak down im referring to the grapple claws, which are split with a hydraulic cylinder for each claw. Where the hydraulic lines attach to machine arm, when i disconnect the inside aux line, the grapple claws will stop in their tracks and wont continue their downward motion. When i reconnect the movement begins again. When i disconnect the outer line nothing happens and the claws continue their downward motion. So i would assume the issue pertains to that inside aux connector’s path through the system.
Back up even further. How is the grapple built. When the cylinders are drifting, are they extending or retracting? Which hose goes to the rod end and which goes to the head end? Try swapping the hoses over from side to side and see if the fault persists.
Grapple cylinders are extending with this issue, and when im clamped tight on material they wont stay tight so they lose their hold and will retract a bit. Cylinders are plumbed correctly. When i roll back on the thumbwheel they retract and when i roll forward they extend. Each Aux line at quick connect comes to a T and then go to the corresponding ends of the cylinders. Ive bypass tested the cylinders and they are not bypassing.
Well if the cylinder drifts down rod-out AND won't hold pressure rod-out AND both cylinders are good then it looks like you have leakage on both lines. I would say the next step would be to remove the control valve and take a look inside the aux section.
Where is the control valve located? Is that the section of the valve block where the two aux solenoids are? The one that midway up the firewall?
Yes. It's the one Nige has been discussing with you. This is the cross section. Follow your auxiliary lines and they should go to ports A and B.
I see. Ok. I will check in the morning and report back. Thank you.
Hello all, came across this post when researching a similar issue with a 4 in 1 bucket. Won't hold in the hold position bucket closes as soon as you let off the roller but will hold open if you disconnect the male coupler on machine side. Did you happen to find a solution to your problem, my 299 is roughly same as yours model-wise. Any information would be helpful. Thank you.