Zx40U3 Hitachi. Bought last fall, haven't used a ton but felt weak. Was going up a bank and realized the boom is weak to the point it won't lift the machine without alot of fuss. Just hits pressure relief. I turned the relief up about half a turn, seemed to be fine. Buttoned it up and still an issue. BUT if I give it just a tad bit of dipper, not even enough to really move it, the boom lifts without trouble. In the book it shows the main pressure relief is adjustable. But mine is different, has a small pilot line sized hydraulic going to it with a T. So something sends hydraulic pressure to the relief and adjusts it. Wondering if that's causing it. Also having related issues with the grapple. I thought it was weak bucket curl, but pretty sure it's the grapple not "backfeeding" when pushed by the bucket. It's a well installed kit that feeds off the boom swing circuit (uses electric diverter valve to switch between the 2). They are using a DCRV110-12N valve on the boom, which I think is supposed to allow backfeed/crossfeed? I've adjusted all over and either it works as normal or makes it no longer function, or function Verrry slow. Thought it was a speed control at first asit acts like that.
Hi You may have an issue in the control valve within the boom segment or possibly with the pilot signal from the joystick for the boom operation that may be causing the weak boom down issue. I'm not sure what the pilot hoses would be on the end of your relief valve as it does not show this in the parts diagram I'm looking at for both the 40U-3 and the -2. The only time I've seen this on a main relief is when a remote solenoid operated low pressure signal can be activated and supplied to the end of the main relief to boost its pressure to a higher setting, otherwise the hoses could be an external drain for the relief valve. The DCRV110-12N fitted to the grapple is a dual cross port relief which may need to be reviewed to ensure that when the grapple cylinder is being opened or closed by an external force, that there is enough displacement in the circuit on the low pressure side of the port relief to allow for oil to flow into. If this relief valve set up is being used on a single grapple cylinder with unequal areas then this type of valve should not be used. Instead, use a 5 port relief with ant cavitation that relieves back to tank instead of cross port. The DCRV110 factory setting is also too low (150 bar) and needs to be increased to at least 265 bar or higher.
Tried to chase down the lines but they blend into bundles of a ton of lines. None of the books I have show it either. It has crane mode, so have to wonder. I tried that and still hits relief. Only thing crane mode does that I can tell is not allow bucket curl, kicks on a tonnage reading on the cluster, which doesn't read any weight,and a strobe light comes on. It's definitely hitting a relief, can hear it. I guess next step is putting guages to see what's going on.
Why would ~2200 psi be too low? It needs to be less than the bucket curl relief right? That's 3200 psi I believe.
main relief is 3550 psi in the circuit diagram and the port reliefs are 3840 psi so you would normally want your grapple to match those port reliefs.
I'm not understanding. If the bucket relief is 3550 (left my.computer at the shop so can't check), the grapple relief has to be less right?
Not necessarily. when using the grapple or any other function besides swing, that operation should relieve at the main relief of 3550 psi at end of stroke or when stalled, but if the grapple is not in use and it takes a shunt from the ground or another object, this will cause an internal hydraulic shock wave which needs to relieved back to tank. As the control valve is not in operation, the control valve is therefor a dead end and the shock wave must then pass through the overload relief / port relief if one has been fitted (such as the DCRV110-12V). If port relief is set too low the attachment can be slow to operate or weak to clamp and hold. If the main relief or port relief is set too high there is a risk of damage to the attachment during operation or under shock load conditions. Some attachments require lower operating pressures in which case the port relieves will usually be set to this requirement and can sometimes be provided with the attachment.
I looked it up. Main relief is 3550 Bucket relief is 3840. I assumed all functions went through main relief?
may have to do some tests with some pressure gauges. Let us know what you find if you get the issue sorted and if you need any help just post back.
I have pressure and flow guages, just had to order hoses. Someone decided they wanted them more than me apparently. Least my flow gauges didn't walk off, the bigger one was $6 or 700.
Ok. Guage on thumb....this is at "normal" rpm (green zone on the throttle). A PITA too, the fairly expensive kit I have only had 1 -6 JIC. Has -7... I have no idea what would even use that? Thumb cylinder dead headed... Open 2000psi. Close 2500psi. That's with the cross relief adjusted all the way in for open (max spring tension on the relief) and all the way out for close. (Min spring tension) I had to screw in the close so the cap could fit, that set it to 3250psi. Not sure what it SHOULD be at. I was guessing 2500-3k area. Close the bucket against the thumb till bucket stops... (hits bucket relief) 1st - 4500psi Open and close again... 2nd - 4000 psi 3rd - 3800 psi No idea why it wouldn't stay the same. I tried that twice as it seemed odd (so 6 times total), and checked with a different gauge. Same results. Also, after moving the thumb (open or close) it holds about 1500psi, even after I shut it off and checked a couple hours later. As soon as the valve is pushed it drops to a few hundred psi, but instantly hits ~1500 when I let my foot off the valve. Cross relief is DCRV110-12N I also tried it flipped around with the "motor" ports fed from the valve and the "valve" ports going to the cylinder. Just started wondering if by chance it was installed backward. No difference. If I back both relief screw almost all the way out, maybe 1-2 turns in, the thumb doesn't work right. Keeps slowly closing and won't open. Any ideas? I've spent hours trying to research and understand how it should work and it's just made my brain spin! I don't understand how the bucket curling can make it not relief.
I would suggest that its probably best not to open and close the bucket against the thumb ( apologies as I thought you had a clamshell type grapple). This is because of the DCRV110-12N valve you have fitted to the machine in combination with the diverter valve. This cross relief valve relieves from one side of the thumb cylinder to the other side of the thumb cylinder which can be an issue because due to the displacement capacity of the bore side of the cylinder verses the rod side, a hydrostatic lock will occur and the only way for the oil to escape is for the oil to try and push its way past the diverter valve or the main valve bank port reliefs back to tank, providing that the thumb is operated on the swing boom offset and you divert to operate the swing boom. If it helps I can draw you some example hydraulic circuits to show you the difference and how it affects the setup. Kind regards
Sorry. I may have called it a grapple. I work in forestry and have used grapples for many years. Brain keeps calling the thumb that I talked with my Dad and he said the same, said needs something that relieves back to tank. Ideas on best approach on that? I searched for a 5 port cross flow, doesn't seem to be a thing? Standard Relief between the valve and thumb? Put it on the extend side so it would flow to tank as it's pushed in by the bucket. The crossflow would allow the cylinder to flow oil from blind end to rod end as well? IE set cross flow to let's say 1500psi, added relief to 2000. I checked and only have the main setup relief for this circuit. Only boom, stick and bucket have added reliefs. Could replace the swing/thumb valve body section with one with a relief. The machine has an extra section, but no reliefs.
Here is an example of what you are looking for. Their are a large number of manufactures that make these types manifolds supplied with cartridges. Any hydraulic or hose repair shop should be able to find this for you if they don't already stock it on the shelf.
Thanks!
Looks like Sun Hydraulics makes one. Would it make more sense to pull the valve body apart and add a section with relief valves?? I can't seem to find part numbers, only finding complete valve banks.
Adding additional control valve sections would be great but due to cost and time required it may not be the best solution. From what I can see in a parts breakdown, your machine has an option kit for either 1 or 2 auxiliary sections that can be added to the main control valve but these additional sections are very expensive. In order to add a section you would need to purchase the spare section, relief valves, tie rod kit and sectional seals/orings. If your machine has a spare unused section that requires relief valves then this would be a good option to set up for your thumb The other cost effective option is to fit a 5 port cross line relief valve to your existing circuit as mentioned before. SUN Hydraulics manufacture high quality cartridge valve components out of the USA and across the globe. Their components are reasonably priced and the manufacturing quality is excellent. here are some part numbers I found online with list pricing in $USD on some of the items Hitachi ZX40U-3 Main Control Valve Spare section relief cartridge - P/N 4708396 - $701.94 each Hitachi ZX40U-3 Main Control Valve Spare section only without relief valves - P/N 4707039 - $2,689.98 Hitachi ZX40U-3 Main Control Valve Complete + 1 spare section + reliefs - P/N 4679273 - $12,966.02 Hitachi ZX40U-3 Main Control Valve Complete + 2 spare section, no reliefs - P/N 4702533 - $13,970.49 SUN 5 Port X-Line relief RDFA/CXFA - $489.61 Reliefs with Aluminum block (2015 catalogue pricing) SUN 5 Port X-Line relief RDFA/CXFA - $624.25 Reliefs with Steel block (2015 catalogue pricing) Kind regards
Ouch. I may just add a relief instead, I'd be around $100-150 with hoses. Have a spare section but it has no reliefs or even pilot plumbing. That 14k price is crazy. That's near what the whole machine cost!
those extravagant prices were listed on the John Deere parts online store for US. " https://shop.deere.com/us/ " Genuine prices for parts are very steep. As long as the thumb can relieve to tank and also draw oil from the tank it should work fine. Note that relief valves and control valve spool types do leak down over time some so the thumb will drift down over time if it is not stowed and locked away.
It does that already, but it takes days. Same if I leave the boom in the air, might drop an inch or two overnight. My idea with a to tank relief on the blind side is the existing crossover will allow blind side to rod transfer, and excess blind side oil (pressure) the to tank relief would handle. Won't work if the thumb is forced the other way but I can't think of many ways to even do that. I think would be into it maybe $200 between relief and fittings and to tank line Did find a few 5 port cushion/crossover, but all are from England, so British pipe and are around $350 with shipping. so haven't decided exactly yet.
I think this is 5 port? https://www.flowfitonline.com/uploads/PDFproducts//CV53.pdf
If you can get it all to work for $200 then your on a win, maintaining and upgrading hydraulic equipment can be an expensive process!
That's for sure! Everytime I need even just a new line it makes my wallet whine! I've setup a few smaller systems, like redid a bunch on a firewood processor, tuned an old street sweeper into a brine dispenser for winter, refitted new with broken "hasn't been available for 20 years stuff", but definitely still learning. And there's often a dozen ways to do something, some maybe easier and "cheap" and others crazy expensive. Spent some time talking with my Dad, he was a millwright at an OSB mill for almost 40 years and he figured it out around same time as I had posted on here. But wasn't too sure how to fix it as he really knows industrial stuff, not excavators... and even harder through pics vs seeing it in person.