What are the set screws with lock nuts below them? They are not shown in the CNH 35 loader diagram. I'm still trying to stop my bucket leak down creep I posted about 2 weeks ago and will begin to trouble shoot the valve circuit. Thanks, David
n175h, those screws are on secondary relief cartridges. They need to be adjusted with the aid of a hydraulic hand pump - DON'T play with them - that won't fix creeping hydraulics. If you play with these you will affect the digging ability of your machine & possibly bend boom cyl rods. Did you check the cylinder hydraulics as was suggested on your earlier post ?
Yes, no creep toward the up position, only down. That is the only test I've done. I've been busier than a long tail cat in a room full of rocking chairs, so I haven't had time to be too intimate with my "hoe", lately. David
Is that with the hoses disconnected & plugged?
Those are what we call port reliefs, they are in there to protect the machine from shock loads when the valve is in neutral. There should be two for each valve section, each one only protects one side of the circuit. If one is leaking it can cause drift in one direction. Two things to do. 1. mark the position of the set screw and back it out several turns, be sure to count the turns, activate that circuit a couple of times, then reset it back to original position. sometimes a small piece of trash can get stuck and by taking the tension off it can get blown out. 2. If they are the cartridge type, swap with one next to it, check for drift, if drift has stopped, that port relief cartridge is most likely the problem, may just be o ring or a piece of trash stuck between the needle and seat. They can be set with a hand pump. normally they are set higher then the main relief, in order to set them without a hand pump raise the main relief temporarily, bottom out the circuit you are working on, set the port relief pressure to spec, then lower the main relief back down to spec. The main relief is a 2 stage relief which maintains a pretty even pressure and allows high flow at Hi or lo idle, the port relief is a single stage, and the pressure will vary somewhat with RPM, also will restrict high flow and generate more heat, so set it with the oil heated up to operating temp and at low idle.
No, it was the suggestion to see if it would creep closed when on the ground while attempting to push the machine wheels off the ground.
I would suspect seal/packing wear in one (or both) of the lift cylinders. The tesing for this is way easy compared to messing with the valve body. Sounds as though someone gave you this advice in the other thread. I had a drift (down) issue in one of my tilt cylinders. I was told to extend the cylinder to the end of it's stroke (all the way out). Remove the hose (at the cylinder fitting) that would be the return when in this position (the one closest to the rod, or the shiney part) and use hydraulic force to try to extend the rod further. Obvioiusly it can't go any further because it is already all the way out. What you are looking for is the amount of oil that is coming out of the open fitting. Some oil is normal (not many seals are perfect), but a lot of oil indicates that oil is bypassing the seals. Bad cylinder seals usually only drift down (with gravity). Upward drift would indicate a valve issue. My seals were so bad that I could hear the oil passing the seals and didn't even have to remove the fitting.
Those are you SRV's (Secondary Relief Valves) On your particular machine they are a screw-in cartridge type pilot operated relief valve, which as the name suggests, you screw them in to fit and screw them out to remove from the control valve without altering their adjustment. I won’t go into the pilot operated type as it's not relevant here. Their exactly the same type as the MRV (Main Relief Valve) but pose a completely different function due to their location and pressure setting. The MRV limits the maximum pump supply pressure and the SRV limits the maximum possible pressure peak in the service line. The SRV is always set higher than the MRV, for example - MRV set @ 320 bar, SRV set @ 350 bar. On your machine, as can be seen in the photo, the SRV for the bucket circuit is the 2nd from right. They are not adjusted with a hand pump, they are adjusted on the machine by firstly adjusting the MRV pressure setting to be higher than the SRV (otherwise the pressure gauge will read the MRV pressure unless the SRV is set lower than the MRV) then stalling the function out and adjusting. With machine's that have 2 or more SRV's (not applicable in Dave's case) the gauge will only show the pressure of the SRV with the lowest setting, so they have to be done slightly differently. The reason they are not adjusted on the bench with a hand pump is because of the large difference in flow characteristics. I have seen it first hand, and it's not an accurate or common practice. In some circumstances it gets close, but never spot on. Some manufactures recommend doing it this way, but I don't care what anyone says, it's poor practice. You will never get the flow characteristic the same as the machine. Before we start jumping to conclusions and pulling his machine apart until we find the problem, how about we start with the basics? Does it drift under its own weight or only when you use it as a hoist or grapple? Are you able to get some photos? In the meantime, read this... Is the control lever in neutral and is there any free play? Are there any external leaks at the pipes, hoses, cylinder etc? You need a spec for your SRV pressure and you need to verify that it's within the spec. Perform a cylinder bypass test - I would use an IR thermometer first and then verify by disconnecting the hose or pipe. Is the spool neutralising? If all these turn out to be ok then the problem can be caused by too much internal wear, damages or cracks inside the control valve.
n175c Just thought I would put up a some specs for you Note a couple of things 1) there are hand pump specs & 10gpm specs - which are different 2) most of the pressures (hand pump) are lower than main relief in particular note boom down (A Port) = 900 psi This is so when you pull dipper through trench, it will force the boom to rise - If you remove this valve & mix it with another - say a 2600 psi swing relief - you WILL bend the boom cyl rods. :drinkup