When any hydraulic function (loader/backhoe/stabilizers) is operated a load is left on the engine. At idle it's really obvious that the whole backhoe shakes. At higher rpms there is a whine and soon the hydraulic resevoir is over-filled with air/oil and it loses hydraulic power. A pressure gauge on the pump fitting shows 375 psi before anything is moved, 3700 psi when any hydraulic cyl. is activated, then 2500 psi after the handle is released. That 2500 psi won't release until the steering wheel is moved. Just a small movement of the steering wheel immediately stops the vibration/drops the pressure back to 375 psi. I replaced both over-pressure relief valves on the backhoe valve block with no improvement. A t-fitting with a ball valve on the right side inside of the frame seemed to allow air from either of the top inlets out of the bottom of the T. If you can solve this for me I would be grateful and send you some of the best peaches from Hood River, Oregon. Thank you.
1st Welcome! 2nd When did this problem start 3rd I would ask for the hydraulic schematic 4th I would say 3700 seems really high 5th I would say I'm a little confused about the reservoir getting over filled with air/oil AND the T-fitting 6th I would say if you have a few minutes, read this. Was a problem I had. HeavyEquipmentForums 7th I would say this forum is awesome! A lot of smart guys here!
I think Blueboy is on the right track with # 4 and 6. 3,700 does seem awfully high, but the relief spec is 3,625 so the pump at full stroke would account for the difference. My guess is the pump should destroke at a bit less than 3,500 though, that's your problem. Go to the parts catalog at jdparts.com and look up "hydraulic pump controller", then find it on your hydraulic pump and see if you feel like digging into it. That's where I'd start, especially if you can find evidence somebody "fixed" anything, but the operations and test manual would be the "by the book" way to do it. I don't have any idea what the Tee fitting is, but the fluid aerates and overheats causing the overflow, because the pump is running over the relief, and maybe there's moisture in the fluid? A little more history on the machine and problem never hurts.
Yeah, without knowing any more than what's been posted I would say that: 1) The pump is either set too high or the controller is somehow defective. 2) It's a load sense system that's working, but either the controller is sticking or there's a problem in the load sense logic where it's holding pressure instead of bleeding down to 375 which is the lead pressure if you will, pump will always try to stay 375 ahead of the load pressure being sent to it on the load sense line. 3) If you're talking about a small tee with a ball check inside it, that's the load sense circuit, it should not have air in it. First guess is the pump is sucking air someplace? 4) There's a small tee coming off the stabilizer valve, appears to be the bitter end of the backhoe load sense line, the end of it would seem to go back to the hyd tank. The description states: "Tee Fitting 1 (W/ ORIFICE)" so I'm guessing this is supposed to be the bleedoff for load sense pressure, pretty sure this is plugged, you should check it. That should get you started, figure out which adjustment screw is which on the pump and try backing one out a half turn at a time, see if the main pressure comes down. As Delmer says it should be at or below 3,500. Call the dealer maybe they'll give you the spec.
I was thinking along those lines about the reservoir getting over filled. If your machine has a filter between the pump and reservoir I would check it and look for any possible leaks that would be letting air into the system. A bad hose, even a tinny hole or crack in the line can let air in. You said the pump was whining, that's never good. Pump cavitation is a serious problem that can wipe out the pump if not corrected. My system does not have the filter there but on the return side. Dynahoe seems to think it’s better to suck in debris rather than starving the pump of oil. Delmer mentioned about moisture, to much water in the system will gunk up a filter.
Blueboy, Dynahoe is not the only ones that don't use suction strainers. Especially with piston pumps. While contamination will damage them, cavitation will destroy one quickly and completely. The trick is to keep contamination out of the tank, and let return filters capture anything that might come loose in the system. On your machine Dynahoe used a really unusual setup, they actually have a gear pump at low pressure supercharging the piston pump to keep it happy...
Hey Lanway, I saw 2 other 1900's on the inner web besides mine and it is definitely unusual. So hayman964's 410E has a load sensing line? Should be easy enough to get the pressure down. Speaking of hayman964, where is he? Maybe he's trying to make sense of my post.
Thank you Blueboy, Delmer and Lantaxco. Please excuse that this is my first time posting on a forum--so in addition to knowing little about my backhoe, this internet help is new also. I am surprised at the immediate offers of authoritative advice, this is awesome. Thank you. My 410E has been doing this vibration/quit with steering input, thing since I bought it from a gov't surplus over a year ago. I use it mostly for loading haybales with the loader end so the vibration is usually relieved with steering quickly. I have used the backhoe end for extended periods in the past and the vibration was there but it didn't seem to be a problem--though if it was idleing afterwards, I'd reach back to tweak the steering wheel to make it idle smoother. The vibration seems to have gotten worse lately--to the point where about a week ago after using the backend for a couple of hours it lost hydraulic power and the reservoir level went from middle to full, and had turned grey. I suspected water (I had been in some) but the sample I drained soon turned yellow overnight as did the reservoir sight tube. It only did the grey/over fill that one time, but the vibration is there all the time, though at cold start-up it's only noticeable when I run a function to its end stop. I think once it warms up the vibration occurs with any action, especially after hitting an end stop. The tech manual states 3625 psi. at the pump. When running the loader end to a stop at 2000 rpm I got 3800 psi, lots of vibration and when the handle was released, still vibration and pressure dropped to 2650 psi. Turning the steering wheel slightly dropped the pressure to 375 psi and the vibration ended. On the backhoe end I got about the same thing only max pressure was 3700 psi at 2000 rpm and 3600 psi at idle. I appreciate you time/knowledge, and hope I provided the info you all requested, Thank you, Adam I have the tech manuals, but couldn't find any reference to my problem. The schematics and jargon all are over my head. My local Deere dealer mechanic advised me to check the two backhoe relief valves and that T with the check (I think lantraxco called it the load sense circuit). I couldn't tell if any were really stuck/sticking so replaced the valves. The T fitting the mechanic had me blow air through to make sure it would not allow air straight through, only out the tee--which it did.
Okay... double check the tech manual, scan and post some pages if you can about the pressure setting. The mentions I can find online say the relief is set to 3625 and the compensator in the pump should always be lower than the relief cracking pressure. The tech manual will tell you which adjustment screw is for the high pressure setting on the pump, and also what the low pressure standby should be, 375 sounds fine to me but who knows what Deere had in mind? What pressures are the relief valves you replaced? Look for that tee I mentioned coming off the stabilizer valve, I would think it has the two smallest hoses on it, pull it out and make sure the orifice in it isn't blocked, this bleeds oil out of the load sense system back to tank so the signal falls off quickly. Might be why the pump is not destroking. I'm no expert but if you want to scan and email the schematics I would be happy to look them over. [email protected]
I'm not familiar with this system so take it for what it's worth. The technical manual is not going to describe your symptoms exactly, you have to be able to narrow the problem down and use the manual to check out your suspicions. If the steering uses the same system as the loader and backhoe, and it seems like it does, then the steering valve could be leaking until you move it a little. I don't know steering valves well enough if or how that could happen, but it would be easy enough to investigate. Go through the steering section of the technical manual. If that doesn't help, try to start it up and let it run with the load and vibration going, if the steering valve or the backhoe valve are leaking they will warm up quickly. How do the hydraulics feel while working? Are they smooth and powerful when moving? and only vibrate at the end of the stroke, and afterwards?