• Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

Kobelco keeps blowing drive motor shaft seal

Akssize

Member
Joined
Jul 13, 2020
Messages
8
Location
carterville il
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.
 

Junkyard

Senior Member
Joined
Jun 5, 2016
Messages
3,621
Location
Claremore, OK
Occupation
Field Mechanic
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.
 

Akssize

Member
Joined
Jul 13, 2020
Messages
8
Location
carterville il
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!
 

Tones

Senior Member
Joined
Mar 15, 2009
Messages
3,059
Location
Ubique
Occupation
Ex land clearing contractor, part-time retired
Some photos would be a huge help to us and you Akssize.
 

uffex

Senior Member
Joined
Jan 23, 2012
Messages
4,464
Location
Lincoln UK
Occupation
Admin
Good day
Most machines have a case drain filter is that the case it could be missed.
Kind regards
Uffex
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
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.
 

Akssize

Member
Joined
Jul 13, 2020
Messages
8
Location
carterville il
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.
 

Akssize

Member
Joined
Jul 13, 2020
Messages
8
Location
carterville il
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.

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.
 

Tones

Senior Member
Joined
Mar 15, 2009
Messages
3,059
Location
Ubique
Occupation
Ex land clearing contractor, part-time retired
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.
Is the seal blowing into the motor or planetary hub ? I've had both and each requires a different fix.
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
I afraid that you have something broken inside the motor.
 

Akssize

Member
Joined
Jul 13, 2020
Messages
8
Location
carterville il
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)
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
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.
 

Akssize

Member
Joined
Jul 13, 2020
Messages
8
Location
carterville il
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.
 

Akorn

Member
Joined
Nov 29, 2019
Messages
5
Location
USA
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.
 
Top