We have a JD 490E here in the shop, that after getting the hydraulics hot the lift circuit slows down badly. If we deadhead another circuit at the same time while trying to lift it will act normal. All other circuits seem to be normal at this time. My customer did say that it has done this in the swing circuit before. Any input would be greatly appreciated. Thanks.
I had a 290D that did the exact same thing. It would work great for 30 minutes or so then get real slow on the lift circuit only. Dealer looked at it, we rebuilt both cylinders, replaced main control valve, beat heads against the wall for 3 years, until I gave up and sols it. Probably doesn't help you much, I just wanted to tell my story.
humm.... worn controll valve, internal cylinder leak?
Cylinders OK, trying some testing on proportional solenoid valve. Going to check variable compensator valve after that. Hopefully I win soon. TY
I assume this is a load sense system-if this was in heavy industry(I know its not but that where I spend most of my time)I would suspect the load sense feedback from this lift circuit. We use a "shuttle valve" that will send the load pressure back to a pump, sometimes the ball in the shuttle valve will stick and block the flow and the pump stays on low pressure standby. I think you guys may refer to these as "resolvers". Maybe this will help, Tom
Thanks for your input, we will see what we get TY. Jeff
Ended up being proportional valve being bad, had to replace old one wouldn't adjust according to specs. TY