This topic contains 6 replies, has 5 voices, and was last updated by Joe 1 month, 2 weeks ago.
- March 8, 2013 at 5:03 pm #25913
My superK has weak hydraulics. I have to hit the throttle hard to get the bucket to raise, can’t even get enough hydraulics to lock the hoe in the up position. Cant raise the bucket at all with a load of wet snow in it. Power steering is weak
HOWEVER, when I bottom out a cylinder on the hoe, my bucket operation returns to normal, OR if I bottom out the bucket cylinders I can get good operation of the hoe.
I”m guessing I”ve got fluid bypassing something in a valve or valve body but have NO idea where to start looking.
No hydraulic leaks from pump, valves or valve bodies.March 9, 2013 at 4:46 pm #28747
Hi Brad, I’m not familiar with Case equipmment, however, I am familiar with Cat equipment hydraulics. Is this a load sensing hydraulic system with a small pump controller valve mounted to the implement pump housing? I’m wondering if maybe you have a load signal resolver double check valve in one or more of your hoe functions that is stuck open. The steering system on Cat machines generates a load signal that is tied in with the implement signal resolver network. A hydraulic schematic would help in identifying the type of load signal system that you have. In a typical Cat load sensing system, each of your hydraulic functions, hoe and loader, has a double check valve that sends a load signal to your pump oontroller on the variable displacement implement pump. The purpose of the load signal network is to select the highest working pressure of the activated functions, and send that signal to the pump as a load signal. The load signal tells your pump to up-stroke and provide more flow. The fact that you can get some of your functions to work by activating other functions is a clue that would be consistent with a load signal problem. Often, each block in the control valve will have its own double check valve load signal resolver that you can inspect. You can look at a schematic and the sequence of flow through the control valves to gain some clues as to which function’s signal resolver is faulty. For example, if your bucket curl function doesn’t work and you simultaneously activate a second function that is downstream of the bucket curl function in the load signal network, then your bucket curl function would start to work. However, if you were to activate a second function that is upstream of the faulty bucket curl function, your bucket curl function would still not work, because of the faulty load signal double check valve diverting flow and the pump controller not getting a load signal.
As far as diagnosis, taking some temp readings with your infrared gun might provide some clues. Areas of the hydraulic system that are hotter than others might be an indication of internal leakage. Is the problem temp dependent? Does the problem get worse with hotter oil? Is your pump hotter than the rest of the system? Obtaining a hydraulic schematic might help you too. Locate your load signal resolver double check valve in each oontrol valve section and inspect them. Usually there is a priority valve that ensures the flow demands of the steering system are met before providing flow to the implement system, but a faulty load signal network could cause the steering sytem to be affected by a signal problem in the implement system. If you are comfortable using pressure gauges safely, it would be a good idea to measure your load signal as well as signal relief setting, and other pressure settings.
You might have pressure compensator spools in each control valve section instead of signal resolver double check valves. In that case, a pressure compensator spool could be sticking. You’ll have to identify the type of load signaling system that you have.
I’m not familiar with the specific type of hydraulic system on your machine so hopefully someone else on here can provide some better machine specific diagnostic ideas. Hopefully, I don’t lead you astray with these ideas. Good luckMarch 24, 2013 at 8:29 am #28776
is it possible to check the delta pressure !! i mean the pressure readings on your load sensing line and the readings on the variable displacement pump output!! if there is a gap between the two readings !! that remain the same during operation !! maybe this can help !! its just a suggestion because im not so familiar with that !! because we tried it in our excavator !! for classic load sensing !!March 24, 2013 at 8:40 am #28777
as we do plumb pressure gauge on the pumps output !! and the load sensing line !! to compare there readings !! if there is a maintaining gap during operations !! to see if your load sensing system is not working well !!April 16, 2013 at 5:25 pm #28788
Not sure if you got your Super K fixed yet? This is a tandem gear pump system with one main relief valve in the loader control valve. The loader control valve also has a flow control valve or priority valve for steering. This unit should be hooked to a flow meter to isolate the issue. If the steering relief valve or flow control valve act up you can get this symptom. As you rev the engine up you increase GPM (gear pump RPM increase GPM increase) This system is also open center so when you bottom out the hydraulic cylinder you are also backing up flow to the rest of the system. Your problem is likely in the flow control valve if the pump passes a flow test. If your problem got worse when cylinder bottomed out I would guess the pump coupler or pump spline as these units have stripped the pump splines. Hope you have it fixed already and if not I hope this helps.August 9, 2018 at 4:00 pm #47652
My problem is the front loader tilt. I had a seal leaking. I replaced both seal during my spring maintenance. I changed all filters and fluids and now the tilt won’t hold pressure. Worked fine before that.October 29, 2018 at 12:13 pm #48798
I have a same peroblem.. hoe can only be lifted when i turn the steering to the left or right..