On excavators, swivel joint problems can cause your travel motors to seem weak or perform unpredictably. If the problem is your swivel joint, then replacing the travel motors won’t help. In this Shop Talk Blog post, we are going to review what a swivel joint does, how it can affect your travel motors, and how to track down the real source of your problem.
Here are a few more Shop Talk Blog posts you might find helpful ...
- Troubleshooting Final Drives -- Eliminating External Issues
- What's Wrong with my Final Drive Motor?
- Is Your Final Drive Weak, or Stuck in High-Speed Mode?
What is a Swivel Joint?
Swivel joints go by several names, including rotary manifold, rotary union, center swivel, and center joint. On hydraulic excavators, the swivel joint makes it possible for the housing to turn without affecting the flow of pressurized hydraulic fluid to the travel motors.
Mistaking Swivel Joint Problems for Travel Motor Problems
Sometimes a problem with the swivel joint can affect the performance of your final drives. You may think it is necessary to replace your final drive, but the problem is with the swivel joint. Replacing the final drive won’t solve the problem. It seems that after about 5,000 hours the swivel joint seals on most machines tend to start leaking. After a while, the hydraulic motors may no longer be receiving all the hydraulic fluid they need.
What you may perceive is a weak or malfunctioning motor, often on just one side. But the problem isn’t with the motor -- it is with the swivel joint. If you have an excavator with a blade, you may notice issues with both the blade and the travel motors. The swivel joint also directs fluid to the control the blade, which is why you may also see the blade affected.
Final Drive versus Swivel Joint
Swivel joint leaks can be internal or external. You probably won’t know you have an internal leak in the swivel joint until you notice a loss of power in the travel motor(s). That is part of what makes diagnosing a swivel joint problem so hard.
One way to determine if the problem lies in the travel motor or the swivel joint is to check the case drain flow out of the travel motor. What you need to do is disconnect the case drain line and cap it. Capping it keeps hydraulic fluid from leaking out and prevents contaminants from getting into your hydraulic system. Next, run the travel motor, stalling it out so your tracks don't move. Monitor the flow from the case drain line.
If your motor is in good shape, then you should see only a small amount of case drain flow. If you see a lot of flow (on the order of two to three gallons per minute), then you’ve probably got a final drive problem instead of a swivel joint problem. Remember that you can check your machine’s manual to determine what the correct range is for case drain flow.
Conclusion
If the travel motors on your excavator seem to be weak or unpredictable, then you might have a problem with a leaking swivel joint. Swivel joint leaks can keep your travel motors from getting the pressured hydraulic flow they need to function correctly. If you do have a swivel joint with leaking seals, then you may not need to replace your travel motors. Keep this in mind when you are trying to figure out what's wrong with your final drive.
Texas Final Drive is your partner in providing new or remanufactured final drive hydraulic motors from a single mini-excavator to a fleet of heavy equipment. Call today so we can find the right final drive or hydraulic component for you, or check out our online store to find your O.E.M. manufacturer brand motor now.
