Kobelco keeps blowing drive motor shaft seal

[12ValveHyundai]

Hello, did you find a solution to this problem? I am having identical issues with a old Hitachi. Did it end up being the overload relief valves on your machine?
I took apart my drive motor and everything seems to be fine but my shaft seal keeps blowing in towards the reduction gear motor. Case drain line appears to be clear to tank. Any help would be appreciated. Thanks.

Have you checked the relief pressures at the pumps? It's usually pretty easy. If you don't have gauges you can pick up a cheap set on amazon for $100, they're well worth it. If your case drain is fine (confirm this, it is the usual cause of this problem) and the pumps are relieving at the correct pressures then my bet in both cases would the swivel joint (turning joint, rotary manifold, or whatever else your manual calls it). The teflon seals inside it need to be replaced periodically. In extreme cases grooves can be worn into the cylinder and then the whole thing needs to be replaced. I can't really explain why it does this, but it seems that pressure ending up where it's not supposed to be when it's not supposed to be there can blow those seals. I had the same problem. The swivel joint was easy to rebuild, seals were $200 and I resealed it in an hour on the tailgate of my pickup.

 

[Tones]

A very simple way of checking the motor condition is to do a casedrain flow check. With the hydraulics wormed up remove the casedrain line from the motor. Then screw a hose into that port and place the other end into a bucket. Now restart the machine and with the track STALLED run the engine up to WOT,engage the track motor and hold it there for 1 minute. Now shut it down and measure the amount of oil in the bucket. My guess that 5 litres is good, 10 or more litres is bad.
To much flow creates pressure and that's why the seal blows.

 

[lantraxco]

The relief valves just dump from one main port to the other, back and forth, so unless there's something odd about this motor, it won't affect the case drain flow or shaft seal. As John C. said, motor issue is almost certainly the cause. A used takeout is one option, or it is possible you just need pistons and plates. Some very common failures are the piston slipper feet coming off, or a broken slipper foot retaining plate allowing the piston slipper feet to cock sideways and come off or disintegrate. I would assume since it drains the tank once the seal opens up that there is very little restriction in the drain circuit, but you might try blowing air through it, with the tank cap off to allow the air to escape.

Oh, if this has a parking brake under that round cover with all the bolts, it *could* be that the brake piston seals are duff and blowing too much oil into the motor case. It just occurred to me I had a Hitachi with that issue around thirty years ago.

 

[Akorn]

Ok guys, thanks for all the help I really appreciate it, you guys all know your stuff because it was spot on. I have watched the case drain flow back into the tank to eliminate that as a possibility. The diagnosis ended up being confusing because one blow out was my human error I believe. After taking the track motor off one more time I looked at it and every piece very closely. This time it had broken pieces. It appears the swivel joint small bearings can only go one way. They appear multidirectional at first glance but after closer inspection the way I reinstalled it allows a possible bind of the joint due to the bearing being backwards. Very hard to notice and almost hard to believe. Finding parts is impossible but I did salvage a primary pump awhile ago and saved my old one. The track motor cylinder, swivel joint and bearings and piston are identical part #s as the components of the main pumps. So I was in luck for parts. But that’s not where it ends. The first blow out was likely caused by the brake seal like you mentioned lantraxco. Now that my floating seal is blown I see I have a small drip. After replacing everything but the floating seal the slow drip must be my brake seal.
The work never ends on these old machines, next I guess I get to see what a brake piston seal repair is like. But I must say, I dug a water line trench with this excavator yesterday at my cabin so maybe it’s a winning battle.