We have a 621D that keeps loosing hydraulic functions ( all loader controls and steering ) this problem is intermittent and happens more often when cold. typically goes away after restarting the machine a few times and will usually function fine the rest of the day but not always. any help would be appreciated thanks in advance.
Gear pump? On a simple open center gear pump system, that is oil starvation for the pump because of a collapsed hose, or a suction hose air leak, and/or a plugged suction strainer. I don't know what a 621 has, that's just my guess.
I will check that out this morning thank you.
Both the strainer and suction hose appear to be fine. The filler cap on the hydraulic tank was plugged but I don't believe that could cause our problem?
Sounds like your having a load sense issue. You can check your load sense at the test port on the main control valve. Since the issue is intermittent, and seems to fix itself, its likely a sticking spool, or shuttle valve. There is a LS shuttle in the main control valve that could be sticking. The pump controls may be sticking also. The other issue could be low/no pilot pressure. Check your pilot pressure, theres a test port by the accumulator. If your machine has a hydraulic quick attach, you can lose pilot pressure through a internally leaking quick attach cylinder
Thank you for the imput we will go that route next. I am thinking I will have to try removing all the valves and cleaning them, since bringing it in the shop where it's warmer it hasn't stopped working and so far all of our pressure tests have been within tolerance.
Best of luck finding your issue. Your tests will only give meaningful results during the issue. What was pilot pressure and pump pressure during the issue?
I haven't been able to test it while it's malfunctioning.
I was finally able to test it today. the pilot pressure was 83 and pump pressure 36 when it was acting up. After restarting the machine the pilot was 445 and the pump was 780 at idle.
The suction hose and strainer were both good I replaced the fill cap on the tank. Cleaned or replaced all the spool valves, check valves, and relief valves in the main valve body. It has not changed the issues with the machine any. Still at a loss on this.
Do you have the hydraulic quick attach? Is the machine acting up more often now? The pressure readings when its acting up show that your losing standby pressure. This could be caused by a sticking spool in the pump, or you are losing load sense pressure, possibly from the LS drain spool or LS relief. A pilot pressure loss could also cause this. To eliminate the pilot side, use the pilot lock, and see if the pump standby pressure comes back. Also please measure your LS (load sense) pressure.
It does have the quick attatch set up but its no longer in use. The rams have been removed and the hoses plugged. I will get these readings later today. Thank you for your help!
i've tried several times today but I can't seem to make the loader malfunction. I am going to leave it outside overnight and see if maybe it acts up in the morining when its colder. I can't say if its acting up more or less often I don't have any information to compare to.
The loader spent the rest of the week out in the ( not very ) cold weather and has yet to malfunction again so it's on its way back to work until it stops again. Thank you for your support!