Hello all, have a cat 289c, SN-JMP02158. This machine is having an issue with low main hydraulic pressure and would appreciate some input before pulling the trigger on new parts. I have done pressure testing by the documentation attached to this post and overall the machine will only make 2800 psi at the very best (right after fire up with cold oil). After running machine for 20min it's all the way down to 2000psi. Have checked main pump and aux pressures with same results as well as even adjusting the relief on the pump compensator and load sensing relief valve. I also removed the valve to check for debris in the screen of the solenoid and no issues there. With also having cut the hydraulic filter open and finding no debris, I guess my question is, are we looking at a new load sensing relief valve or new pump? It seemed odd that the pump did not respond to any of the relief valve adjustments. Thanks again for any input.
More diagrams I was using for reference and the load sensing relief valve/solenoid.
Did you do case drain “bucket” test? It will not be in the manual.
If you isolate the pump, plug the discharge port and run flow control all the way down - you essentially turn the LS pump to PC pump. That’s how A10VO runs in old telehandlers. Back out pressure compensator ( big screw), run flow compensator all the way, plug/cap discharge, attach gauge somewhere before plug/cap. Start an engine and start screwing pressure compensator in. See how far it’ll take you. The only thing - this test will not tell you volumetric efficiency of the pump, it will only confirm achievable pressure
Can you post hydraulic diagram of the machine, it’s easier for me to work with that.
I appreciate the info, I have not tested how much is being pushed from the case drain, I can try that next once I get oil back in it. I unfortunately don't have any other hydraulic diagrams of this machine to work off of.
If there’s not much coming out of case drain under load. You might do isolated pump test, adjust pressure compensator to 3350. Then reconnect the system, set the margin and see what it does. If you can’t achieve required pressure in isolated test, but case drain is not that great - you can check the spring in the pressure compensator. Those Danfoss springs sometimes brake. But let me ask you: was this pump on machine for long, or just recently replaced? Those pressure compensator springs comes in increments. If pump was recently replaced, it might be the case that wrong spring was installed.
My customer just bought this machine last fall so not sure on any service history, it does have 5k hours on it. The pump is black with cat I'd tags. I have attached a pic of it. Hard to say if it is original to the machine or not. I will preform your recommended tests on it but it's looking like a new pump is in order.
Yes - she was replaced before. Those hand written marks to the right in the picture don’t come factory. Well a run isolated test.
Will do, hopefully get to it tomorrow. I'll update you afterwards. Thanks for your time
The implement pump looks like Danfoss Series 45 - J frame. Drive pumps are Dandoss H1 tandem.
After further testing, pump proved to be worn out. New pump has been installed and working well. Thanks for your help and time.