Hi all, I own a 450C with a backhoe attachment and have recently came across an original JD control valve (Very Lucky)for that hoe and I have decided to try installing a thumb/log splitter on the boom. I made 16" 3/8" bolts for the assembly and I have put the entire valve body back together. I made a few fixtures to put air pressure in the system to make sure I have no leaks in between the bodies. When I did this, I have air coming out of both ports on the swing boom valve. There are 4 different stiles of valves on this body and only 1 swing valve. I pulled apart the relief valves and I see no issues with anything internal. I have a service book but there is not a ton of good info or checks that I don't think really helps me. It looks to me like when that valve is in center position it has flow but I was really hoping someone with a bit of experience on this forum might give me a kick to help me understand this. Again I "think" that pressure might need to be there with this drum type of backhoe, but I could very well be wrong. Anyone have a thought? Also I am only checking this with 130ish psi and just FYI I don't think there were any issues as of 3 weeks ago with this swing.
Welcome to HEF Rufus . I would say leakage at the swing valve ports is not normal. Pull the swing spool and check it for scoring.
Another possibility is a crack in the valve body.
Hi guys. Thank you so much for the reply's as I am really struggling with this. I see no signs of gulling or cracks in these bodies, and this seems like its full air pressure not like a leak or something of that nature. If you look at this one schematic, doesn't it appear that oil is going to the cylinder? I am just wondering if air is not enough pressure to open the bypass.
Did you rotate the spool from it's original position when you reinstalled it ? A spool that badly scored will certainly pass air through it. Especially of the bore looks like the spool. Oil may not leak in it like air does.
I am not sure but do not think so and I feel zero grooves in them like the score is minimal and you could be right about the oil passing. With that said I did pull it all back apart and I isolated just these 2 valves. I then applied air to them (1 at a time) and I also rotated the spool in both of them, and it had zero change. Both valves are different from the rest and do the exact same thing leaking out of the same port. I applied pressure, rotated the spool (no change), then I pulled out the spool (operated it like on the hoe) and flow stops to that port and is applied to the other, I then went back to zero position then air comes out of that port then I push in the spool and full air comes out of that same port. Keep in mind this is not like an oring leak its a full blast of air. I keep thinking that schematic shows flow in neutral position doesn't it?
The schematic of the boom section you provided,the spool is NOT in neutral position , the spool is shifted to the right. I’m grasping at straws here but…the swing section only has a unique lift check valve assembly #16. I wonder if that lift check design is allowing air to leak from both ports when the spool is in neutral. . .
Maybe that's why I am confused as I thought all schematics were shown in neutral position unless specified. That check valve I pulled apart and its pretty simple and it looked fine to me. Just to confirm, I have 2 identical valve bodies on this that have the check and relief valves and the rest do not. I am only getting leakage from 1 port on each valve, and both are the bottom port which kinda makes me think this pressure is supposed to be there, but I honestly don't know. All the other valves are fine (I think). Think I will put everything back together and see what happens. Thanks again for your posts!!
It may not be an issue. I only say that because I have a 931B Cat with a backhoe that is very similar open center hydraulics. I had to remove the backhoe to fix the swing pivot. All the hoses except for the stabilizers and swing had to come off. One of the stabilizers creeped down on the ground. When it was time to put the backhoe boom back on the swing post I figured I could start the machine, lift the stabilizer and back up about 2 feet. Even with the control valve for the stabilizer pulled when I started the engine, oil was flying out everywhere!! I thought my control valve bank was completely shot. I got the stabilizer up enough and shut the engine off. I used my skid steer to push the machine backwards. It was baffling to me how much oil was shooting out. I hooked all the hoses back up and there were no issues at all. I figured the oil shooting out had near zero pressure and the valves had a certain amount of leakage built in for lubricating purposes or something. Normally you'd think if oil is shooting out the cylinder ports, the cylinder is going react by either extending or retracting. Nope, everything worked as it should. I think before you look into damage with the valve bank you should hook all the hoses up and see if there is actually a problem.
I really hope you are correct Dave. I am glad to see you have had this same issue and your right, you would think this would move a cylinder but this is possibly where the Bypass inline comes in.
There is no pressure and once the hoses are connected and filled the fluid just goes through the valve bank until a spool(s) are activated.
That sounds correct. Not sure why they did only these 2 valves this way, but maybe its to keep the drums full of fluid. I wish the service manual was a tad more specific on these. We shall see. Hopefully within a few weeks and will re-post my results. Thanks again for all the input.
It might be normal internal leakage to keep the spools lubricated.