Evaluating a Used CAT 304.5 Mini Excavator with Hydraulic Concerns

[MikePhua]

Introduction to the CAT 304.5
The Caterpillar 304.5 mini excavator was introduced in the early 2000s as part of CAT’s compact equipment lineup, targeting contractors, landscapers, and utility crews. With an operating weight of approximately 10,000 lbs and a 40-horsepower diesel engine, the 304.5 offered a solid balance of power and maneuverability. Its zero-tail swing design and hydraulic thumb compatibility made it a popular choice for tight job sites and light-to-medium-duty excavation.
Machine Overview and Purchase Considerations
A prospective buyer recently evaluated a used CAT 304.5 with 2,800 hours on the meter, priced $3,500 to $4,000 below typical market value. The machine appeared physically tight and free of external leaks, but several operational issues raised red flags. The buyer intended to use the excavator for light-duty farm work, including tree transplanting, road maintenance, and general cleanup—approximately 150 hours per year.
Hydraulic Performance Issues
Several hydraulic anomalies were noted during inspection:

• The dozer blade could lift the machine even at idle, suggesting strong hydraulic pressure in that circuit.
  
• However, the boom and arm required full throttle to lift the machine, indicating possible pump wear, flow restriction, or control valve imbalance.
  
• When turning, the left track spun under load, but the right track did not. In straight-line travel, both tracks engaged, which may point to a drive motor imbalance, final drive wear, or pilot control inconsistency.
  
• The upper structure exhibited a slow rotational drift to the right—approximately two feet per hour—suggesting internal leakage in the swing motor or center swivel joint wear.
  

Undercarriage and Track Condition
The tracks were described as poor, with signs of heavy wear from operation on hard surfaces. While the buyer considered them serviceable for limited use, worn tracks can affect traction, grading accuracy, and resale value. Replacing both tracks on a 304.5 can cost between $1,200 and $2,000 depending on brand and installation.
Cost-Benefit Analysis
Although the machine was priced below market, the list of concerns could quickly erode any initial savings. Potential repair costs include:

• Hydraulic pump rebuild or replacement: $2,000–$4,000
  
• Final drive or travel motor service: $1,500–$3,000 per side
  
• Swing motor reseal or replacement: $800–$2,500
  
• New tracks: $1,500 average
  

Even conservative estimates suggest that repairs could exceed the $4,000 discount, especially if multiple systems require attention. For buyers without mechanical experience or access to affordable labor, these costs can escalate rapidly.
Recommendations Before Purchase

• Hire a qualified heavy equipment mechanic to perform a full inspection
  
• Conduct a hydraulic pressure test on all circuits
  
• Check for error codes or diagnostic history if the machine has an electronic control module
  
• Test all functions under load, including travel, swing, boom, and blade
  
• Factor in downtime and parts availability if repairs are needed
  

Conclusion
The CAT 304.5 is a capable mini excavator with a strong reputation, but used units with hydraulic inconsistencies and undercarriage wear require careful evaluation. For mechanically inclined buyers seeking a winter project, such a machine may offer value. For others, the hidden costs could outweigh the initial savings. A thorough inspection and realistic repair budget are essential before committing to purchase.