I have a K907DLC, the drive motor keeps blowing the shaft seal. I changed the return filter. Put new seal in and blew immediately. Drains all hyd fluid from tank after it blows. I’m thinking the DM is getting way to much pressure. Could it be a relief valve? The other side seems fine. Any ideas would be great.
Relief valve is bad
What kind of case drain pressure and volume are you seeing? Sometimes if a seal is blowing it’s due to excessive wear allowing case drain pressure to build up. A quick and dirty check is to make a short hose and put it on the case drain line and run it into a bucket. Should take a minute or two to fill the bucket if it’s in fairly good shape.
I’m with ^
Not sure on the case drain. I pulled the caps off of the position where the drive valve is on the main control valve and the right one (bad side) had fluid in it and the left one didn’t have fluid in it. Going to blow air through the return line tomorrow. Case drain? Are you talking about the return line from the drive motor? And where is the relief valve for the drive ports? Are they on the main control valve? Thanks!
Some photos would be a huge help to us and you Akssize.
Good day Most machines have a case drain filter is that the case it could be missed. Kind regards Uffex
As I recall your machine model is a pretty old work horse. Your explanation of the problem needs a bit more information. Where is all the hydraulic oil draining to? Is it going outside of the machine and onto the ground or into the final drive that the motor is driving? All hydraulic motors have an extra line that allows the slight amount of leakage in the motor to just drain back to the tank, i.e. case drain. The line is usually a lot smaller than the feed line to the motor. Any motor case drain flow will generally be less than a steady flow, more like droplets. A high flow of oil through the case drain hose will indicate that something is broken inside the motor. Motors that drive systems that have the potential of running away, such as a track drive motor going down hill, will have systems inside the motor to prevent that. The relief valves and all the rest of that stuff are nearly always designed to be inside the motor itself. Case drain filters are usually a low pressure low flow affair. One would generally cut them open and check for loose metal particles being caught that came from damaged motors and such. Almost all case drain filters are designed with a bypass mechanism installed in them so they don't blow up when something bad happens.
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For your reference.
Thanks everyone! The replies are helping so much. Here are some pics,
The fluid is leaking out on the ground. I don’t have the final drive gears and cover in yet till I can figure out why the shaft seal is blowing. I’ve put two new seals on the shaftAfter replacing the shaft bearing and the float seal.
Fluid is going thru the final drive side. The original problem was the fluid was leaking from the float seal and drained all the fluid on the ground. I took final drive gear out and found the motor shaft seal was blown causing the float seal to pressurize and then blow. So i removed the final, and motor off and apart put a new float seal, shaft bearing and shaft seal, put it back on thinking cause was a bad seal and worn bearing. After installing all back together except the gears in the final and the final cover on. Filled It with hyd fluid, got the air from lines. The boom, bucket, swing all worked. Then i went to move the drive motor and the fluid blew the new seal out. So then thought it was case drain filter, i put a new case drain filter on and put another new shaft seal in added new hyd fluid in and tried It again, and it blew the seal again immediately. That’s were I’m at now. That’s about best i can explain.
Is the seal blowing into the motor or planetary hub ? I've had both and each requires a different fix.
I afraid that you have something broken inside the motor.
I took Both the Overload relief valve out of motor and 1 seems to be good and the other 1 didn’t move very freely. I cleaned it up and gonna give that a chance i think. ( crossing my fingers)
That will be bad. Ive already looked all over for a used motor. And got. Quote for $7500 to rebuild. Any suggestions?
It's known around here as "that is what you get for what you got." You have a big and very old machine that you likely didn't pay much for and now it is broke. The reason you didn't pay much, is that it costs so much to fix and parts are scarce and very expensive. There is no easy or cheap fix if the motor is in fact broke. Either learn how to fix it yourself or spend the money it takes to fix it. You could also just block off the hoses to the motor and run the machine on one track and use the boom and swing to pick up and move the dead track.
We’ve had this machine for 25 yrs or so. Been a pretty good one. Yes i know its time to upgrade.
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.
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.
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.
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.