I own a New Holland L785 it has 4500 hours and has been a really good machine. I have a problem with the boom hydraulics in that it will not stay down when lowered. The boom wants to bounce as if it had air in the lines instead of oil. I can't seem to find the problem or haw to cure it. Any suggestions?
Are the pins and bushings loose. Maybe piston is coming loose off of rod
Might be coming down fast enough it's sucking air into the rod side of the boom cylinders, or bad piston packing, will it power down and lift the machine okay?
Well, I have checked all the pins, all tight. the boom will stay where I want it until I start to try to dig or grade in hard material, then it is like, you're grading on rubber, bounce, bounce, bounce. The odd thing, it does not do it all the time and then it will take a spell and act up for hours. Sometime I can grade or dig and everything works perfect but when it starts the boom bounce as I call it, just drives me nuts when it does. I thought maybe there is a bad internal seal, letting fluid pass by inside the cylinder and not letting the cylinders hold position but why would it not do the bounce all the time. I do however think it is getting worse and me with only one nerve left, know what I mean. Thanks for any advice on how to check this out.
It sounds like it's only doing it when you are pushing down/trying to dig. Then it could very well be the deals in the cylinder(s) because the force of digging is trying to extend them and a leaking seal will allow fluid to pass from the rod side to the piston side so to speak since there is a bigger void created on the piston side. When I say piston side I just mean the side of the piston opposite of the rod. There's more volume in that side due to not having the rod thus fluid can leak from the rod side to that side via a bad seal, but not the other way because the rod side cannot accept the oil. Once it leaks some, it will equalize and stop the drift. May be why you notice it only sometimes. There may be times the seal doesn't leak for some reason also. It's also possible something else in the system is leaking as well though.