My excavator is giving me its first real issue since I bought it in May. When I bought the machine, I found that the right track motor was leaking hydraulic oil, so I opened up the cover and found that the top and bottom relief valves (#21 on motor diagram) were leaking oil. I took the relief valves out and found that the largest o-ring (#2 on the relief valve diagram) was completely shredded on both relief valves. I replaced the o-rings for the top and bottom valves with the proper o-rings, and it worked fine from May till today when I noticed a small puddle under the right track motor. The exact same two o-rings were shredded again on the same right track motor. Why is my machine shredding these o-rings? Edit: Attachments aren't working, so I'll post links to the diagrams instead Brake valve/Track Motor Diagram Relief Valve Diagram
Are you using replacement o-rings from Deere or from a standard o-ring kit?
I got the replacement O-Rings from John Deere and carefully installed them, putting electrical tape over the threads when sliding on the O-Ring to prevent any damage to the O-Ring.
That's a curious problem that it blows the o-rings on both relief valves. That's what made me think it was the incorrect size o-ring. Do the relief cartridges fit into a hole that has a bevel at the entrance of the hole like diagram below?
I'll check when I get back to the machine, I'll be away from it this week. One odd thing I found was that the repair manual said to tighten the valve on to around 300 or 400 lb/feet (I forgot the exact number but it was something like that). I had never found anything else using o-rings that require such very high torque, but I did as the manual said using a big torque wrench. Could it be typo in the service manual? Could that very high torque have caused the damage to the o-ring? Thanks, Sultan
Well, since your not near the machine now, but will be, I'll throw out my thought. First, I'm not sure what type of o-ring seal connection we're working with, which is kinda important to figuring this stuff out. It's just curious to me that both reliefs blow the o-ring. A proper o-ring seal of any type and of any torque should handle as much pressure as the system will put out. The fact that it blow both relief o-rings is what makes me think the o-ring is not correct, but I can't say that for certain, especially considering your getting the o-ring from Deere. Very Weird. All I can say at this point, if the ports that the reliefs go into has that bevel at the entrance to the port, then it should be a "Boss o-ring" type seal configuration. The Boss o-ring seal requires using 900 series o-rings, like 568-901, 568-902, 568-903 and so on. If you use 568- o-rings that are not -900 o-rings, they will not work. Also, it's best to use 568-900 o-rings that are 90 durometer (stiffness of o-ring). 70 durometer are much softer and don't perform as well in this application.
Thanks for your ideas ATCO, I would be lost without your expertise. Blowing both o-rings baffled me. I have a vague recall of the hole having a beveled end like your diagram but I'm not sure. It is unlikely but possible that the dealer gave me an o-ring of the right dimensions but wrong type. I'll see when I get back to the machine. Thanks again ATCO
Baffles me as well bro. If the parts page shows you need part # XXX-XXX, then the o-ring should be correct. Beats the hell out of me. But the fact that proper o-ring seals will hold, by design, what system produces is what makes me puzzled. And that both reliefs blow this seal, I'm scratching my head. I have seen poorly machined bevels on o-ring boss seals that lead to seal failure, but it would be very unusal for both millings of the two relief ports to have faulty millings. Very unusal problem you have. Keep us updated.