Hi to all. Firstly, thanks for this incredible source of information. Nevertheless, I've gone through the threads but cannot seems to find something relating to my issue. Yesterday I was setting up my backhoe stabilisers and for once went to the full extension. As I hit full extension, the sound from the hydraulics changed (no rattling or anything, just different) and I no longer had any hydraulics, nor in the hoe nor in the front loader and no power steering. I can lower the hoe boom and the front loader by gravity but other functions anr non responsive. I initially thought that the coupling to the pump may have failed but upon checking all is fine in the front end. I suspect perhaps that the main relief valve is stuck open. Do any of you have any advice on how to check this and / or if the issue could be elswhere? Thanks
The main relief valve is a definite possibility and would be something to check. You need a hyd. pressure test kit and the service manual is helpful. Are these something you have access too? If you know where the relief valve is, try taping it gently with a hammer while the machine is off. It may reset.
Hi. Thanks for the answer. I don't have the test kit but I do have the manual. While investigating a little further, with the engine off, I tried pressing the mini quick connect where the test kit gauge goes and I can easyly open it until oil drippes out. Strangely I can also do this with the engine idling. My question would then be, should I be able to do this with the engine idling? Even in a open circuit, should there not be at least a little pressure preventing me from pushing open a quick connect by hand? Also, I removed the main relief valve very briefly and took a picture of it. It seems fine as in the seals are clean and smooth (although I don't know what jammed open would look like!!!).
You would need to take the relief valve apart to see if it is stuck. The manual should give instructions. Did you confirm that the hyd. oil level is sufficient? Ebay has hydraulic test kits.
@Ben76 I would be taking a closer look at the pump coupling. Sometimes the pump shaft does still turn somewhat, but it stops when the slightest load is applied to the hydraulics. If the main relief was stuck open, there would still be some hydraulic movement - be it without any real force or pressure.
Pump shaft may have broke #9 Pump splines may have stripped and coupler is still spinning #14
My Case 580sk has the opposite problem. The boom will come back faster than before. The boom will not go down. Then the boom swivels do not move. No leaks. Happened suddenly. I replaced the belt just a day before and that looks fine.