My Koehring 6620 LC-5 excavator was warmed up and moved perhaps 200 yards when the left track started losing power. Thinking something broke, the operator called me and I asked him to leave it for me to look at it. Six hours later, I hopped in, and it drove fine for another 100 yards until we went up a 15 degree grade. Then the left track went dead, but the right track and the swing motor were all fine. The boom would only raise at high RPM and even then VERY slowly. Ditto for the dipper stick and the bucket curl features. I shut off the machine and checked fluid levels. Hydraulics were four gallons low. I topped it off and nothing changed. I then went through an air purging process and things got MUCH better, but still my dipper stick and bucket cylinders are acting up. They move nearly fine at high rpms. At mid and low rpms, the dipper stick will uncurl to vertical and then will get stuck there for about a minute before SLOWLY uncurling. Applying bucket curl out with dipper stick curl out results in near instantaneous response from both the dipper stick and bucket - until the bucket is fully uncurled. As soon as the bucket is uncurled, the dipper stick goes back to slow operation. Raising RPM's primarily solves the issue, though there is still a delay in the dipper stick when it reaches straight vertical from a curl - it seems to 'fall' into straight vertical and then gets hung there for 1-2 seconds. The local heavy equipment tech firm service truck came out and thought that the issue was the hydraulic filters needing to be changed and that what was happening was that the system was going into filter bypass under heavier hydraulic flow. His second option is an issue with the ram of the dipper stick. I posted on an OLD thread looking for hydraulic filter cross references for this machine as I wanted to change filters anyway (I've had the machine two years, but only for maybe 30 hours of use), but wondered what you guys thought. Could clogged up filters cause this issue or should I be looking elsewhere?
I have a 6620-LC-6 I bet you have more problems than just clogged filters, hopefully the filter cleaning will fix it but it is more likely pump problems. Good thing is the pumps are still easily repairable and the company that advertises here on the forum will rebuild it...
In order for the filter theory to be true each side of the pump would need its own. Not likely. Sounds like the pump has a control issue or you lost some piston shoes/ valve plate is cracked /etc. You need a specialist who works on hydraulics to determine what your next step is. With the age of the machine you may as well pull the pump for preventative maintance in the worst case. If you run it longer as is the cost usually explodes.
This, combined with mike bramel's posted information (thanks!) makes MUCH more sense. What company is it that you are referring to on here that rebuilds them?
I think it http://www.excavatorhydraulicpumps.com/home.html They priced a complete pump rebuild for the exact pump you have for 3900.00
Awesome! Thanks! Now it's just a matter of whether I'll be able to get filters for the thing - so far I am concerned given the MinnParr is saying that they only have 1 or 2 in stock for most of them needed and NONE in stock for some others (the main hydraulic return). They are verifying for me now whether they can get them at all. Of course, though, they are not providing cross references. WIX or someone surely makes something. The trouble is finding out which one meets the filtration and flow requirements.
I think I ended up getting all the filters except the big hydr filter from Napa of which it was still good so we only cleaned it out. Mine also has the Isuzu engine like yours.
Do you possibly have the NAPA part numbers?
The pump is a Rexroth A8V107. Koehring part number 730 8650 We sell them for $3250 Rebuilt exchange Or you can send it in and we'll bench test it for you and let you know what, if any, issues it has. I used to run a Koehring dealership and we were never able to cross the return filters. I got rid of my filter cheat sheet for Koehring years ago..do you have the part number? Is it 708 6449 ?
Found it in the other 6620LC-5 thread. 730 4341 is the return filter assembly 730 4342 is the filter element itself Try a Baldwin filter distributor. Even though I was never able to cross this filter, they may have it catalogued now. Good luck!
Finaldrive, That is a good price for that pump, I will contact you next time, did not realize you had the hydraulic pumps too. Thanks
Yes sir. We stock every Korean excavator pump as well as most Kobelco, Case and Linkbelt. Over 200 supported excavator models. All NEW and complete. Plus we have dismantled almost 4,000 machines and have a huge Rebuilt inventory. I'd list all of the other new product we have, but I think I'd violate the forum rules for advertising