Yanmar 4 Ton Excavator Track Problems and Solutions

[MikePhua]

History of Yanmar Compact Excavators
Yanmar, a Japanese manufacturer founded in 1912, became a pioneer in compact excavators by introducing the first mini excavator in 1968. Its machines quickly gained global traction due to their fuel efficiency and adaptability in confined spaces. By the late 1990s and early 2000s, Yanmar excavators had spread across Europe and North America, with annual sales of compact machines surpassing 50,000 units worldwide. The 4-ton class excavators, such as the Yanmar Vio40 and Vio45, are especially popular in construction, landscaping, and utility sectors because they balance digging power with transportability.

Common Track Problems in 4 Ton Excavators
The undercarriage and track system of a Yanmar 4-ton excavator endure extreme conditions. Frequent issues include:

• Track loosening or derailing
  
• Excessive wear on sprockets and rollers
  
• Hydraulic track motor leakage
  
• Uneven travel speed between tracks
  
• Track tensioner failures
  

Statistics from fleet operators show that undercarriage maintenance accounts for nearly 50% of lifetime operating costs on tracked excavators, making this system one of the most expensive to maintain if neglected.

Track Loosening and Derailment
One of the most reported problems is the track frequently coming off during operation. This happens due to:

• Insufficient track tension caused by a failing grease-filled tensioning cylinder
  
• Worn sprockets unable to properly grip the track links
  
• Damaged or missing track guides
  
• Operator technique, such as sharp turns on uneven ground, accelerating wear
  

A quick test involves checking whether the track sags more than 35–45 mm between the top rollers. If sag exceeds this, tensioning is required. In severe cases, a complete sprocket replacement and inspection of the idler may be necessary.

Hydraulic Travel Motor and Final Drive Concerns
Uneven track movement—where one track moves faster than the other—often signals hydraulic motor or final drive issues. Possible causes include:

• Internal hydraulic leakage reducing torque output
  
• Worn planetary gears in the final drive
  
• Contaminated hydraulic oil damaging seals and bearings
  

Routine oil sampling can reveal metal particles, an early warning of gear wear. Manufacturers recommend oil replacement every 1,000 hours, but high-dust environments may require shorter intervals.

Track Tensioning System Failures
Yanmar uses a grease-filled track adjuster to maintain proper tension. Failures occur when:

• The grease fitting leaks, allowing tension to drop
  
• The recoil spring weakens with age
  
• The cylinder rod corrodes, preventing smooth adjustment
  

Field mechanics often carry a grease gun with high-pressure fittings to quickly re-tension tracks. If grease leaks after pressurization, the adjuster must be rebuilt or replaced.

Preventive Maintenance Practices
To extend the life of Yanmar 4-ton tracks, operators should follow these best practices:

• Inspect track tension daily and adjust as needed
  
• Clean out mud and debris after working in wet or rocky conditions
  
• Avoid excessive counter-rotation which accelerates sprocket wear
  
• Rotate track chains from left to right after 1,000 hours to even out wear
  
• Record track hours separately from engine hours for accurate service intervals
  

Case Study Example
A contractor operating a Yanmar Vio40 in utility trenching reported constant derailment of the left track. After inspection, it was found that the track adjuster had a slow grease leak, causing daily tension loss. Instead of replacing only the seal, the company opted for a full adjuster rebuild, costing around $650 in parts. After repair, derailments stopped entirely, and productivity increased by 18% over the following three months.

Glossary of Terms

• Track Adjuster — A hydraulic or grease-charged device that maintains track tension.
  
• Final Drive — The gear and motor assembly that delivers power to the tracks.
  
• Recoil Spring — A spring that absorbs shock and keeps the track properly aligned.
  
• Sprocket — A toothed wheel that engages the track links to drive the machine forward or backward.
  

Summary
Yanmar 4-ton excavators, while efficient and durable, are vulnerable to track-related problems if maintenance is neglected. The most common failures involve loose tracks, tensioner leaks, and uneven drive power. Proper inspection routines, timely repairs, and the use of genuine parts greatly extend undercarriage life. For operators and contractors, preventing undercarriage failures translates directly into reduced downtime and improved profitability.