How to Restore Track Tension on a Large Excavator

[MikePhua]

Track Tensioning and the Role of the Idler
Large excavators like the Daewoo 400 rely on hydraulic track tensioning systems to maintain proper engagement between the track chain and undercarriage components. The system uses a grease-filled cylinder behind the front idler to push it forward, tightening the track. When a track falls off, the pressure must be released to retract the idler and allow reinstallation. Once the track is back on, the idler must be pumped forward again to restore tension.
Challenges in Re-pressurizing the Idler
Operators often encounter difficulty when attempting to pump the idler back out. In one case, a hand-operated grease gun failed to build sufficient pressure, stalling midway through the process. This is a common issue with large machines, where the volume and resistance exceed the capacity of manual tools.
Solutions include:

• Using a pneumatic grease gun capable of delivering higher pressure and volume
  
• Verifying that the track adjuster is not seized or internally damaged
  
• Lifting the track off the ground to remove weight and reduce resistance during tensioning
  

Terminology Clarification

• Track Adjuster: A hydraulic cylinder filled with grease that pushes the idler forward to tighten the track.
  
• Idler: The front wheel in the track system that guides and tensions the track chain.
  
• Grease Nipple: A fitting through which grease is pumped into the adjuster.
  
• Porta Power: A hydraulic hand pump system used for high-pressure applications.
  

Advanced Troubleshooting and Fabrication Tips
If the adjuster resists pumping despite using pneumatic tools, further inspection is needed. Possible causes include:

• Faulty grease nipple: The internal ball may block grease flow. Replacing or cleaning the nipple can restore function.
  
• Twisted idler alignment: If the idler binds sideways due to frame wear, it may resist movement. Inspect both sides of the housing for uneven travel.
  
• Seal failure inside the adjuster: Grease may bypass internally, filling both sides of the cylinder without moving the piston.
  

In severe cases, a custom solution may be required. One technician fabricated a modified adjuster fitting by gutting the internal check valve and welding a ¼-inch hydraulic coupler to the end. This allowed connection to a porta power hose, using hydraulic pressure to free the idler. This method has been used successfully on trenchers and older excavators with seized adjusters.
Preventive Maintenance and Best Practices
To avoid future track tensioning issues:

• Grease the adjuster regularly, especially in dusty or wet conditions
  
• Inspect the idler alignment during routine service
  
• Replace worn seals and nipples before they fail
  
• Use high-quality grease rated for heavy equipment applications
  

A contractor in Ireland reported that lifting the entire side of the undercarriage—idler, rollers, and sprocket—off the ground made tensioning much easier. This removed all friction and allowed the adjuster to extend smoothly.
Conclusion
Restoring track tension on large excavators requires more than brute force—it demands the right tools, clean fittings, and an understanding of how the idler and adjuster interact. Pneumatic grease guns, alignment checks, and custom hydraulic solutions can all play a role. With proper technique and maintenance, even stubborn adjusters can be brought back into service, keeping the machine productive and safe.