I've had this excavator for several years. It is for occasional use around the farm - nothing commercial. The swing function has always been weak. If I am on a bit of a side hill, it won't swing a full bucket of wet earth uphill, so I have to always work around it. The blade function is also weak - it won't fully lift the machine. I am not sure if the two are related. All the other hydraulic functions are very strong and it will dig through anything, and lift big rocks using the thumb with no problems. I know very little about complicated hydraulics, but am comfortable around machinery and engines. Last year, I brought it to a local shop that does a lot of small excavator repairs. He went through everything, flushed the hydraulics, new filters, etc. and did some engine injector work. He claimed he tested all the hydraulic pressures, and they were all ok. However, the swing and blade are just as weak as before. I am not sure I fully trust him, although he seemed to do nice work overall. I realize that to fix the weak swing, I will have to dig into the shop manual and start working through everything. Again, I am not experienced in this stuff, and would like to find a different, reliable mechanic to fix this. I was wondering if the collective experience here could suggest the most likely source(s) of this problem? Is it likely the pump, or something in a pilot circuit, or the swing motor itself? I do think it odd that both the blade and swing are weak, so I would assume (bad idea) that they are served by a common, weak pump, even though the original mechanic claims he tested them. I like the machine, and overall it works just fine for what we need it for - the occasional pipeline or ditch work, etc. If I could fix this one flaw, I would be happy with the machine overall. OTOH, if everyone tells me this is likely a very expensive problem to sort out, I might just sell it and start looking for another used machine in good shape. I don't have much money in it (< $10K) and the tracks and such are like new. Any ideas of how best to start figuring this problem out?
If you raise the blade up to maximum height upwards with a Tee Tap installed on the hose that makes it go up, a gauge hooked up to the tee tap will record the real pressure available. If the pressure is too low you have either a leaking packing in the cylinder or problem in the valve or source. You could raise it up with the pressure on the hose to make it go up, while letting the other hose shoot into a pail. When it reaches the end of travel the oil has to stop flowing or the packing is leaking. I am just guessing that it is a 1 cylinder blade control. Might be an idea to post your serial number and post a picture of your blade cylinder setup. Simon C
You have 2 problems going on at once. You will need to hook up gauges also with regards to your swing function problem. Someone else may chime in who has schematics on it. Simon C
Umm, can you share hydraulic schematic? it will help much in identifying the issue
Thanks to both of you for helping with this. I have all three manuals (operator, parts and technical), but none of them are all that helpful. I've attached the closest thing I can find to a hydraulic circuit diagram from the parts manual. In the troubleshooting section, for a weak hydraulic function, they keep saying to check the pilot controller. After that of course, I'm supposed to call my John Deere dealer. If the mechanic working on this is telling the truth, then the pressure coming off the pump should be normal. I don't see any obvious hose kinks or such on anything coming off of the two joystick controllers. So perhaps the first place to start checking is in the "pilot controller"? The little bit I know of hydraulics (<0), it might make sense that two of the functions are weak - swing and blade - while the others are normal. I have absolutely no idea of what to begin to look for in the pilot controller - except to call my local JD dealer of course. Thanks in advance for any advice on how best to proceed.
In my world your definitely not supposed to call your John Deere dealer to check the pilot controller. To check the pilot controller means checking the pilot secondary pressure and it is described how to do that in your work shop manual, however thats not prio 1 now. It is very rare to have correct pressure and weak functions att the same time so I suggest you check pump pressure first, most interesting is pump 3. Check the pressure on blade, swing and boom swing both way on each function. Any difference? Also check if the arm or the boom speed increases in light operations when you use a slow function, if so you have a problem with your flow combiner valve in pump 3 section of the main control valve. I do not have access to a hydraulic diagram of JD35ZTS. I have checked a diagram of Hitachi zx35U2 when a wrote this so I might be wrong. In your picture number 2 the pilot hose seems to be attached to the swing pump. Strange.
Thanks for the response. When you say "pump 3" is interesting, do you mean the assembly item 3 in the 2nd photo? I didn't copy the figure legend, but the manual calls item 3 a filter assembly, which appears to run into 6, a solenoid. I am guessing 6 must be the main safety solenoid that would divert the oil flow to the tank or on to the control valve? I know all the filters in the tank were changed, since I saw the machine apart when I visited the shop, when he was cleaning out the main hydraulic tank. However, I don't know where filter #3 is, but I can start rooting around to see where everything is in relation to the diagram. I don't have any pressure gauges and fittings, so I can't do any detailed checking on the differences in the pressure for the blade, swing and boom functions. Your troubleshooting suggestions sound perfect to isolate the problem. At least if I bring it to someone with the proper troubleshooting equipment, I can ask them to check these functions. Being a total novice on these kinds of hydraulics, and finally studying the basic diagrams, I am starting to understand some of the basics. So there is only one main pump in the system? That would seem to rule out a poor main hydraulic pump, since there is good pressure to other functions. As far as controllers, there seems to be only 3 - the two joysticks on the arm rests, and the main control valve. So I can see why the troubleshooting section of the manual keeps saying to check the Control Valve for a weak function (or call JD of course). So that main control valve seems to be where all the action is. I suppose if one of the control valve circuits was bad, it could affect only one or two functions (swing and blade in this case) while the others are normal. At least that sounds plausible to me. If it was simply a weak swing motor, then I don't see how the blade would be affected. At this point, I probably need a competent shop with the right tools, to dig into the problem, unless I wanted to just replace the entire control valve perhaps with a salvage unit, although I have not found many salvage units of these old machines around much. I imagine this valve is hideously expensive and hard to replace? I'll look over the machine again with this in mind, just to see what I would be facing.
You really need 35ZTS Operation and test manual TM1840. You can check the general condition of pump 3 by cycle timing the swing and the blade functions. All tests at done at fast idle and hydraulic oil 120 deg F. Swing Left or Right, 3 Revolutions from a Running Start... 21.1 ± 1.5 sec . Backfill Blade: Raise...... 1.7 ± 0.5 sec Lower... 2.1 ± 0.5 sec.
Hydraulic schematic and legend with basic details in screenshots below. Notice the swing is pilot controlled and the blade and boom swing are mechanical controls. .
Pumps identified below.
Thanks for the diagram and detailed explanation. This is way beyond my shade tree capabilities. I'll probably try to find a local mechanic competent in these excavators. The thing now is how expensive any repairs are likely to get. I can still sell the machine I have, with its weak swing, for more than I paid for it. It does work, and I have dug small ponds and ditches with it - I just have to work around its weak swing and such. I like the machine, but if I wind up putting high $$$ into it, I'd be better off looking around for a newer machine in better condition. I'll need to find a competent mechanic I can trust, who can do accurate troubleshooting, then give me a realistic repair cost estimate. Or I can go to my local, friendly JD dealer!
Diesel Dave, you got me thinking a bit. I didn't think about the pump having 3 sections, but it is obvious now, just like a tractor pump usually has several sections. From your description, it almost matches that pump section 3 could be weak, since it is the swing, blade and boom swing driven by 3. At least, that would be a pretty close match to the symptoms I have. At least, if I find a mechanic, I can discuss it with him, and hopefully point him in the right direction. Without looking anything up, I wonder how expensive it would be to simply find a rebuilt or salvage complete pump, and just replace it myself? I hate to just replace parts, but it might be cheaper for me to go that route, and replace the pump myself, if there was a decent chance that is the source of the problem.
Don't spend a cent without hooking up gauges first and doing comprehensive tests to come to the correct conclusion. Too many fire the parts cannon and still nothing works. Simon C
Yeah, I agree. I was thinking out loud. But at least with the help everyone has given, I can try to find a shop with the correct testing gauges and equipment, and talk to them semi-intelligently about what I want checked.
Dave, maybe I'm missing something here but I can't see any pilot lines going to spool 33 for the swing motor.
There is no pilot lines drawn only power lines, no? Therefore only the manually operated valves have indication of control, not the pilot operated ones I think.
I believe the pilot controls are on a separate drawing as I could not see any pilot control other than the lever on the blade cylinder valve. Maybe I am wrong. Different companies do things differently. Simon C
That is definitely on a separate schematic.
According to schematic above, Pump 3 has no relief valve between the spools so it must be incorporated in the pump, This is also a gear pump so is rpm dependant for flow/speed, I think you can discount the pilot system as the blade spool which uses the same pump has no pilot control. Are you sure that it really is weak? , a pressure test on P 3 will establish this but on the schematic above no pressures are stated.
There is a mistake in the hydraulic schematic in post # 9 . The pump 3 releif is not incorporated into pump 3. See control valve components list below.