I recently had new seals put in both the boom cylinders on my Kobelco SK115SR serial # yy03-05xxx. One cylinder was weaping and I had the other done while the hydraulic shop had it, it operates just fine but now the the boom drifts down if lifted up and also will not hold the machine up if you push down and lift the machine, it slowly lets the machine settle back down. The hydraulic shop said there is probably air stuck since they couldn't bottom out the boom at their shop, so I did that a handful of times with no change. The odd thing is a friend also has a 115SR and recently had his boom seals done (by a different shop) and his machine is doing the same thing, any suggestions would be greatly appreciated!
Either the piston seals are not quite right, or you have maybe port relief issues.
Were they drifting before rebuild? Also there are several outfits making aftermarket seal for those too some good and some NOT so good.
Thanks for the replies. I meant to say it was NOT drifting before the seals were replaced...
Sounds like the poly pack seal could be backwards or the piston seal Isn't correct. Especially since it wasn't happening before
I agree...It really sucks when you try to have a problem fixed and end up with another....ill be visiting the hydraulic shop in person tomorrow, yaaaaaaay!
Yeah, could maybe be backwards, or just too stiff a material that doesn't seal well at low pressures. I recall one Hitachi I worked on, the boom drifted, not terrible but noticeable. With a full cleanup bucket or a vault on the hook it would hang all day and maybe drift only an inch, just because the load expanded the seals better.
maybe you should do a leak off test before going to the hyd shop.. at least have something to go in with..
Hydraulic shops can cut seals to. Usually if you lose a piston packing in pieces, it can make its way back into the control valve. Most of the time, the bigger pieces end up stuck in the load checks, the port reliefs, and sometimes the main relief. I would say the you have internal leakage in your newly resealed cylinder(s).
The seals on the piston end can go either way there is no difference there is just one seal in the center the rest are wear rings or bearings whatever you want to call them. On the rod end if the seal was in wrong it would leak like a stuck pig out the rod.
Well, just to update, I finally finished the job my machine was on and brought it back to the hydraulic shop so they could see what was causing the drifting.....there was a piece of metal jammed in between the packing and the barrel and it gouged the crap outta the barrel wall. Of course they "had no idea how that got in there" and it "must have somehow come through the hydraulic system". Of course it did.... I never could have imagined a piece of metal getting in there, it looked like a piece of slag about the size of a bb from a BB gun but smooshed up, much less getting THROUGH my hydraulic system and wedged in between the seal and barrel, that they just repaired. Especially since I have owned the machine since new and have followed all of the maintenance to a T and have been the only operator. So, I have handled this somewhat diplomatically, I found a used cylinder for $1400, they will go through it, and make sure it's in good shape and repack it,I have bought new suction and return filters and will be there when the old filters are pulled from the machine, if there's no metal in there,they pick up the tab on the cylinder, hydraulic oil, re packing both cylinders again, and the hydro filters....either way, I'm in a bad place and they're in a bad place, hopefully it didn't come from my machine (which I'm 99% certain it didn't) but on the 1% chance it did it seems like it could be just the tip of the iceberg for repairs...
If they're amateur enough to leave debris in your cylinder unlikely they will clean out the valve. So this process may repeat