I need some help & advice on how to check/service/replace the load checks on my NH EH80cs excavator. The s/n is listed in my "signature" section at the bottom of this post. A little background....Despite getting my bucket cylinder & thumb cylinder repacked/resealed not long ago, both those cylinders drift down or out an annoying amount, both when the machine is running but levers in neutral & when the machine is off. There are NO observable hydraulic leaks ANYWHERE, & the fluid is full. So, I'm beginning to suspect the load checks in the main control valve. From both the NH & Kobelco service manuals (I have a PDF of both), there seems to be a total of 13 load checks in various circuits in the control valve. At the bottom of this post I have attached a selected 6 pages from the NH manual: And here is a photo of the top of my control valve: My questions are: Where exactly on/in the control valve are the load checks for the bucket circuit & the thumb (nibbler-breaker) circuit? What's involved in taking them out &/or replacing them?? For example, must I drain all or some of the hydraulic fluid?? In order to help answer my questions, if you would like to download the complete service manuals for the machine, please PM me (start a conversation) & give me your email address & I will send you a link. I really appreciate the help...
Hi, first off I am no kobelco expert. the load checks you refer to are NOT your problem. the purpose of a load check is to support the load while opening the spool valve. this allows the pump oil flow to catch up ,and then move the load A bad load check will show up as a slight drop of the load when the control valve is first moved the only places that could cause your problem in the control valve would be the spool and body condition and the overload reliefs item 62 (I call them line relief valves ) you could try and swap them around to see if it makes any difference. Are you completely sure the cylinders have been repaired properly Mark ps yes I would like a copy of the service manual
/\ Thats the truth
Mark250...As I said in my first post, if you would like to download the service manuals, please PM me (start a conversation) & give me your email address & I will send you a link. In the meantime, I'm thinking about your "load check explanation"...I'm certainly no hydraulic expert...& also how confident I am that the 2 cylinders involved have been repaired properly. Maybe I'll work on trying to test them isolated from the rest of the system....
hi, I would double check your cylinders first if you do not know how we can guide you through the process the bucket cylinder has the rod facing down ,is the bucket dropping down with rod retracting or rod extending when the bucket is curled back Also what is the position of the thumb cylinder rod down or rod up? Mark
Mark250...I sent you an email with links to download the service manuals. Re: cylinders... My bucket cylinder faces down, so the rod extends & the bucket drops as it drifts. My thumb cylinder faces down, so the rod extends & the thumb drops as it drifts. So far I've tried a very simple test on my thumb cylinder as follows: Cylinder all the way retracted (thumb retracted). Shut off valve on the stick for each end of the cylinder. Observed that cylinder extended about 11" in 4 hrs. Assuming the valves don't leak (they haven't when I've taken the thumb off previously), the only way this can happen is oil is bypassing around the piston seal, from the rod end to the cylinder end, & forcing the rod to extend because the area of the piston is bigger on the cylinder end. Right?? So, looks like my hydraulic shop did a crap job of repacking/resealing that cylinder!! Come to think of it, maybe they never even touched the piston seal, just resealed the cylinder....!! humm.... If it isn't so dammed hot tomorrow, I'll try the following test on my bucket cylinder: Cylinder all the retracted (bucket uncurled). Uncouple the hose on the cylinder end, & plug both the cylinder port & the uncoupled hose. With machine running, try to RETRACT the cylinder. If the cylinder actually EXTENDS, then oil has to be leaking past the piston seal, using the same logic as above for the thumb cylinder. I suspect it will!! Maybe this is all good news....mucking around with resealing my cylinders is probably safer & cheaper than having my way with my main control valve. But given my probable past experience with my hydraulic shop, am I going to have to do it myself in order to be sure its actually done & done right?? Boy, that's sad....
Hi sounds like your hydraulic shop stiffed you this is my preferred method to check for faulty cylinders a couple of things to be aware of 1/position the rod at various positions and cap as above ,this can give you an idea if the cylinder is barrelled or has internal scratch's in different parts of the stroke 2/understanding Pascals hydraulic laws will give you an idea of the extremely high pressures that can be generated in the rod end if the seals are OK. This is due to the piston to rod area ratio SO BE CAREFULL On some cylinders I actually install an external relief valve for protection Mark
Good day Please see attached hope you find it helpful. Kind regards Uffex
Additional information. KR Uffex
Just came in from sweating & testing hydraulics...when is the humidity/heat going to subside!! Anyway, I tried the bucket cylinder test as I described above, namely: Cylinder all the way retracted (bucket uncurled). Uncouple the hose on the cylinder end, & plug both the cylinder port & the uncoupled hose. With machine running, try to RETRACT the cylinder. Surprisingly, the cylinder did NOT MOVE!! So, I re-did the same test, except started with the cylinder about 1/2 extended. Then the cylinder EXTENDED about 1/2" more, indicating some initial piston bypass leakage, but did not move further as I levered more retraction. So, how do I interpret that??? When I experience the biggest drift in use is when the bucket cylinder is fully retracted, the machine is in neutral or off. So there is no active retraction pressure on the piston. Could it be that the piston seals that my hydraulic shop used only seal under active, high pressure?? Does that make any sense?? I looked back at the invoice of my cylinder re-seals on 8/15/2012. I transcribed the itemization on the invoice to a spreadsheet, & a PDF of that sheet, as well as a Zip of the spreadsheet itself is attached at the end of this post. Take a look at them. Here are some observations & questions: The "Brand" column I have inferred from the part numbers on the invoice. I don't know if they were actually Hercules brand. I had 2 cylinders re-sealed, so it makes sense that there are 2 piston seals, 2 rod seals, & 2 wipers, BUT I can't seem to group them into the sets for each cylinder, bucket & thumb. The sizes don't seem to make sense. Can you group them?? The "official" repair kit for just the piston seal on my bucket cylinder seems to cost $180.79 from Messicks. See the screen shots below from the parts catalog:
Uffex...I have read the 2 documents you uploaded with interest, several times....I think I now understand that per the schematic you marked up (response.pdf), my machine has a lock valve, in addition to shock valves, in both the boom & arm circuit. But my bucket & thumb (nibbler & breaker) circuit have only shock valves. These shock valves are what Mark250 identified as "overload relief valves", item 62, & they are referred to that way in the parts catalog. Hopefully, I won't have to muck with those....yet.
Good day S Wally Yes 82 we refer to as a shock valve but we are aware that there are many differing terms used sorry for that confusion, not absolutely sure as to your result from the test you made but I have attached a couple of docs. that may support your repair. Repairing cylinders in our experience not only requires sealing to be replaced but often there is a cause as to the failure. Kind regards Uffex
Uffex...I'm hoping Mark250 has some ideas based onmy test results. But thanks for the additional docs...I've read them. Alas, I don't have any hydraulic gauges to use...hell, I don't even know for sure what thread type/size the hydraulic fittings on my machine use...maybe some "Kobelco" thread, vintage 2005?? The thumb is a Geith pin-on, so it uses different threads. Been thinking about the load checks in my system (item 21 on the schematic) & Mark250's explanation that they are merely there to hold the load just prior to raising to allow the raising pressure to build...But what about when the load is at rest, which is when I get drift?? Aren't they also involved?? But maybe they are not positioned in the primary flow path?? I'm getting that sense the more I study the schematic.
Good day S Wally I would endorse Marks explanation, the only components that take care of cylinder creep are those I have highlighted, the valves you refer ensure that the pump gives sufficient pressure to begin the cylinder movement forget these they have no effect with the problem you describe. Note these are on the input side of the main valve not the cylinder side with the main valve closed these are isolated from the cylinder. If you have illustrations of the main valve chest we can point out the actual valves and what functions the are used for. Kind regards Uffex
Hi from your tests it appears that the bucket seals are OK but just to be on the safe side do the same tests using the other cylinder port if that is OK swap your line reliefs over ,As a rule they are the same valve but with different pressure settings and for testing purposes wont matter
Uffex...OK, you, Mark250, & the schematic have me convinced that the load checks can NOT cause my problem. Thank you much for the education!! Now on to the main valve & your offer to point out components...Here are some fresh photos after removal of the RH body panel & pressure washing: For example, where are the overload relief valves (shock valves) for the bucket circuit & the thumb circuit??
Uffex...If it helps, here is a photo of the nameplate on the main control valve: I believe it reads "Nabtesco LF30V00001E2 05-1-1324-5"
Uffex...Here is a photo of the typical hydraulic fitting thread on my NH / Kobelco excavator. Can you identify what the thread name/type/size is??
Good day S Wally My commiserations with your climate here today we 25.5 deg.Cel. its not a good temperature for humans only engines, first may we suggest we begin at the actual problem in that way we can get to the real issue and I hope resolve your problem. I know you are limited with your resources in the way of tools etc. but lets be realistic to diagnose the problem only with our ideas and suggestions is not going to be that realistic so at the least you will need a female & male plug to the hose connectors. OK you don't know the connector size or type but somewhere in the manual you have some specification tat you may quote to a local hose supplier, mean while we will prepare some specific information for you to diagnose your problem so give us a little time and we will make step for step instructions. If you have a complete hydraulic circuit diagram this may well help us if you can post one the Email is [email protected] I hope we can start with fresh minds and resolve the issue. My kind regards Uffex
The coupling looks like a standard Emeto coupling these are a metric olive type used a lot during the 80/90 but if you can copy the spec out of the manual we can be sure.
Mark250...I did the same bucket cylinder test as before, but used the "other" port, i.e.: Cylinder about 1/2 way extended (bucket half curled). Uncoupled the hose on the rod end, & plugged both the cylinder port & the uncoupled hose. With machine running, try to EXTEND the cylinder more. The cylinder extended very slightly (about 1/2") then stopped & would NOT extend further as I levered more extension. To me, this proves again that the bucket cylinder piston seal is NOT bypass leaking. I can't swap the reliefs over until Uffex can identify where exactly they are. Even then, am I going to have drain some or all of my hydraulic fluid to do it?? And what if I could borrow some hydraulic gauges...& get them hooked up properly...would that eliminate having to swap the reliefs?? Also, I'm in the process of getting a plug for my thumb hoses so that I can run a similar bypass test on the thumb cylinder. Based on my previous result in post #6, I expect the test will confirm that the thumb cylinder piston is bypass leaking.
Good day S Wally May I ask are you connected with a on line chat possibility Mac ? Re Uffex
Uffex...I've got the plugs for the Kobelco lines...that's what I took a photo of & what I've been using to do the cylinder bypass leak test on my bucket cylinder. I understand you call this "standard Emeto coupling....a metric olive type used a lot during the 80/90". What's an "olive" type?? I haven't noticed the thread name/type being called out in either the operator's manual of service manual, but I will look again. I will email you a link where you can download my service manuals, both the NH one & the Kobelco one. The hydraulic schematics are in their.
No, no online chat, but we can email, or maybe I could call you, or I could email you my phone # & you could call me??
Hi Wally OK do you have face book? Tim
Duh...I realized I don't need plugs, because I have shutoff valves on the boom on both thumb circuits, so first I tested as follows: Thumb cylinder about 1/2 way extended. Valved off the hose on the CYLINDER end, rod end live. With machine running, tried to RETRACT the rod more. Observed rod retract slightly (about 1/2"), then it stopped & would NOT move in or out as I levered more retraction. Therefore, cylinder piston NOT bypass leaking into the cylinder end, which would cause extension. Then I ran the reverse test as follows: Thumb cylinder about 1/2 way extended. Valved off the hose on the ROD end, cylinder end live. With machine running. tried to EXTEND the rod more. Observed rod extend slightly (about 1/2"), then it stopped & would NOT move in or out as I levered more extension. Therefore, cylinder piston NOT bypass leaking into the cylinder end, which would allow extension. The only way I can explain these results with the reverse results of the static test I described in post #6, is that over the time of the static test the shutoff valves (which were both off during that test) must leak slightly, allowing the thumb cylinder to extend under the weight of the thumb. So, at this point, I conclude that neither my bucket cylinder nor my thumb cylinder is bypass leaking past the piston. The problem has to be in the overload reliefs or the main spool itself. Does everyone agree??
Yes we would endorse your explanation please be aware that main spools do leak not the best method of sealing hydraulic fluid. Kind regards Uffex
here is the spool positions for the bucket and nibbler circuit. if you are not sure just follow the work hoses back to the valve . the line reliefs will be at ninety degrees to the work ports and adjacent to the spool valves
Since my last post, I've done the following: In-place drift tests on all my hydraulic cylinders. Refer to my new thread here: HeavyEquipmentForums Had extensive email exchange with Uffex. Long story short, the root of my problem is that even the small amount of drift I have in my bucket & thumb circuits is due to the lack of lock valves in these circuits. Whereas the boom & arm circuits have lock valves in them & , consequently, have virtually no drift. So, this thread can be considered closed, & I will continue my issue in this new thread: HeavyEquipmentForums