I have a kobelco sk200 and the cylinder that runs the stick won't hold the stick out strait. It wasn't too bad at first but in the last 15 hrs it has gotten a lot worse to the point were it it is hard to load a truck. The stick will stay in place if it is curled back towards the boom but if you put it out strait it will drift back down to its resting point in less than ten seconds. Is this just the cylinder bypassing internally or some other issue!???
Probably a bad piston seal, there's usually one for each direction, but also could easily be a port relief valve, and then there's the less likely bad valve spool and whatever else your particular machine may have in the circuit. The brute force diagnostic is to switch the two hoses going to the stick cylinder thus reversing the function. If the problem remains the same, it's the piston seals in the cylinder, if the problem changes direction along with the hoses, it's a valve issue. You can also usually swap the port relief cartridges at the valve spool after ruling out the cylinder. I am just talking from generic knowledge, I am not familiar with the SK200. :my2c
Good day Alex85 You can find trouble shooting method at excatech.com and its free. Kind regards Uffex
Thanks for the reply Iantraxco. That's what I have been told it is also by a local heavy equipment mechanic. Just sucks cuz it's kind of a pricy fix, but oh well what isn't expensive on these things!
Pricey fix? If you think repacking a cylinder is pricey don't even think about getting the valve stacks rebuilt, lol
Well I kno... It wouldn't even be worth fixing really...but I'd call 1200 bucks expensive enough for me! Lol
If you do only the piston seals and not the rod seals you can do it pretty cheap. All you have to do is remove the rod from the barrel and replace the piston seals. It can be done without removing the cylinder from the machine. It might cost a couple hundred that way. Are the rod seals leaking externally?
Some but not bad at all...but is the port relief internal in the piston? Because I've been told it mite not be seals it could be that.
No the port relief will be in the valve. I would try swapping port reliefs first to see if the problem moves.
Yea I can hear what sounds like fluid going back thru a line on the boom to the machine so it makes me think the problem may not be in the cylinder. Or maybe the sound of the fluid bypassing in the cylinder is just traveling down the line but doesn't seem likely.
If the piston is bypassing as the cylinder extends, due to the difference in area between the rod side of the piston and the full piston face, the cylinder needs more oil on the backside of the piston to fill the hole, so you get oil flowing through a "makeup" check valve up through the line to the butt end of the cylinder. Same would be true if the oil from the rod end is leaking off through a port relief or other valve issue, then you get flow in both lines. As I said before, the first thing I would do is swap the two stick cylinder hoses wherever it's easy to do it, probably at the boom foot. The control will be reversed, but if the problem remains the same, drifting down from the extended position, then it's almost certainly the piston seals. If the port reliefs are easy to get to you can also try swapping those as Mobiltech suggests, being lazy I usually go with whatever is easiest to do first, you decide, lol.
I changed the hoses around today on the piston and the problem stayed the same so it must be the piston seals. So I took it off and I'm gunna take it to a hydraulic shop in the morning where it can be rebuilt. Thanks a lot for everyone's help!
So I figured you guys would be interested to kno what's wrong with my machine. The shop called today and said the cylinder and rod are scored pretty bad and they can fix the rod but I have to buy a new cylinder. If that wasn't bad enough now I probly have chunks of metal all through my hydraulic system! I gotta see how bad the scoring is and check the filters and tank first but man I wasn't prepared for this! It sucks so bad! I haven't had it for 2 months yet and already had all this happen looks like I made a bad decision...
Pretty common when the rod bends it will gouge the tube
They never said anything about the rod being bent I don't beleive it is
Does anyone know how long it should take to flush and clean the hydraulic system on a machine this size? Once the system is cleaned out and filled again is there a good chance I could have more issues with debris in the system or will it be good if it was flushed right? Thanks
Suggest running a hydraulic oil sample, then you will know. I am thinking these particles are in the filter or stuck on a magnet and maybe are not 'in solution', but I try to be optimistic. And if the fluid has high readings, maybe you can run a recirc pump with a fine filter?
Hi oceanobob that sounds like a good idea. The local kobelco dealer said the problem likely started and got worse when the machine was transported. Over time the cylinder got sloppy since the cylinder was all the way out and bouncing on the trailer... Who knows. I think I'll try what you said and change the fluid and filters and flush immediate lines going to that cylinder. How far do you think fluid goes back and fourth in the system when that cylinder is being cycled?
See if you can get a sample from the sump (system) to the oil lab, then after you get the results you will know a lot more about the oil. The oil lab charges us about $15 to do the analysis and we get the results back by email in about a day or a day and a half. We pay up front for the sample and we are given a bottle when we pay. The shipping thing is also figured into the situation as well. Then move forward on the cleanup / filtering / oil changing / etc.
See if you can get a sample from the sump (system) to the oil lab, then after you get the results you will know a lot more about the oil. The oil lab charges us about $15 to do the analysis and we get the results back by email in about a day or a day and a half. We pay up front for the sample and we are given a bottle when we pay. The shipping thing is also figured into the situation as well. Then move forward on the cleanup / filtering / oil changing / etc.
Ok where I could send a sample to be tested?
Around here, I selected the Cat dealer but the other equipment dealers (we only have two others: Case and JD) had the similar program...I picked Cat because the lab is not too far from here and all I had to do was drop off the sample at the local Cat dealer and they took care of the transport to the lab....google shows Holt Cat in Irving serves the Addison area? * Side and off the thread: We were told not to rely on oil samples to buy a piece of equipment as the oil is for trending - but the skip loader from a rental outfit (we had actually written the check for it) had so many particles in the sample the lab thought I had sent them a dupe from something like the bottom of an old waste oil sump! Needless to say they returned the check and said thanks and promptly took that machine to an auction somewhere.....
Oh wow I hope my oil doesn't end up like that...yea I'm close to Milton cat in Bangor Maine and Beauregard equipment one of those should work not sure about the one you mentioned...
Sorry - another Addison! LOL, I found the first one that came up on the search, and it was in Texas. * It will be interesting to see what the analysis shows.
Yea it sure will..thanks for your help oceanobob! I'll let you kno the results.
Oceanobob I told you I'd let you kno the results of the hydraulic oil analysis...I never ended up doing that I figured id change it either way. We found some bigger chucks of metal like (1/8 of an inch or so square) in the filter and the tank but there was no fine metal at all. There were a couple pieces of seals too. We just drained the tank and wiped it all out and removed the metal then cleaned it all out thoroughly with mineral spirits then wiped it out again. I would say most of the metal didn't leave the cylinder. I have put about 20 hrs on the machine since the repair and it has been working great (knock on wood). I am goin to change the hydraulic filter again soon and check the screen. Hopefully I am in the clear now!
For use, the process to get the oil/coolant samples was a bit tedious, but once we figured it out, we can get them done readily with no hassle. Has been an axx-saver and helpful for troubleshooting, etc. Glad to learn your progress; changing the fluid and inspecting the tank are worthy actions.