Auxiliary Hydraulics on Caterpillar 873F Skid Steers

[MikePhua]

Introduction
Auxiliary hydraulics play a critical role in the functionality of modern Caterpillar skid steers. These hydraulic systems provide the power needed to operate a wide range of attachments, from augers and grapples to trenchers and snowblowers. Proper operation of auxiliary hydraulics ensures the skid steer can perform specialized tasks efficiently, reducing manual labor and increasing project productivity. Despite their importance, auxiliary hydraulic systems sometimes fail or work intermittently, causing operational delays and increased maintenance costs.
The Caterpillar 873F skid steer, a mid-size machine introduced in the late 2000s, is particularly known for its versatility and robust performance in forestry, construction, and landscaping applications. Its auxiliary hydraulic system, designed to deliver precise flow and pressure, is crucial for operating attachments safely and effectively.
Development History of the 873F Skid Steer
Caterpillar, a global leader in heavy machinery, launched the 873F model as part of its “F” series, emphasizing improved operator comfort, hydraulic efficiency, and durability. The 873F features a Tier 3-compliant engine, advanced hydraulic systems, and reinforced undercarriage components to handle demanding workloads. Sales of the 873F have consistently performed well in North America, particularly in industries where heavy-duty auxiliary attachments are frequently used.
Importance of Auxiliary Hydraulics
Auxiliary hydraulics extend the functional range of the skid steer. Attachments rely on a steady flow of hydraulic fluid at the correct pressure to operate efficiently. The system typically consists of:

• Hydraulic pump
  
• Control valves
  
• Solenoids
  
• Hydraulic hoses
  
• Quick couplers
  

The auxiliary hydraulic system is typically rated in gallons per minute (GPM) and pressure (psi), with the 873F’s high-flow option delivering around 29–32 GPM at 3,000 psi. Mismanagement or failure of any component can reduce the efficiency of the attachments and potentially damage the hydraulic system.
Common Auxiliary Hydraulic Issues
Operators frequently report three primary categories of issues:

1. Intermittent Operation
   • Symptoms: The attachment works inconsistently, sometimes responding and other times failing.
     
   • Causes:
     • Electrical issues affecting solenoid valves
       
     • Partial blockages in hydraulic lines
       
     • Pressure fluctuations due to pump wear
       
2. Complete Failure
   • Symptoms: Attachments fail to respond entirely.
     
   • Causes:
     • Blown fuses or defective relays
       
     • Damaged wiring harnesses
       
     • Malfunctioning hydraulic control valves
       
     • Low or contaminated hydraulic fluid
       
3. Reduced Performance
   • Symptoms: Attachments operate slower or weaker than expected.
     
   • Causes:
     • Worn hydraulic pump
       
     • Leaks in hoses or couplers
       
     • Air in hydraulic lines
       
     • Incorrect attachment flow settings
       

Electrical System Troubleshooting
Electrical issues are a frequent culprit. The auxiliary system relies on solenoid valves to direct hydraulic fluid. If a solenoid does not receive the correct voltage, it cannot open or close properly. Steps for diagnosing electrical issues include:

• Checking fuses and relays
  
• Inspecting wiring harnesses for frays, corrosion, or loose connections
  
• Using a multimeter to verify voltage at solenoid terminals
  

Hydraulic System Troubleshooting
Hydraulic issues can be mechanical or fluid-related. Key troubleshooting steps:

• Control valves: Inspect for blockages or stuck spools.
  
• Hoses: Check for leaks, cracks, or kinks.
  
• Fluid: Verify proper level and clean condition.
  
• Pump: Test for correct flow rate and pressure.
  

Attachment Compatibility and Considerations
Not all attachments perform equally well with standard or high-flow auxiliary hydraulics. Operators should:

• Verify flow requirements of attachments against the skid steer’s auxiliary specifications.
  
• Understand that high-demand attachments like brush cutters or snow blowers may require high-flow kits or upgraded hoses.
  

Maintenance Best Practices
Preventive maintenance is critical:

• Regularly inspect hoses, fittings, and couplers.
  
• Check solenoid function during routine service.
  
• Replace hydraulic filters according to manufacturer recommendations.
  
• Monitor hydraulic fluid for contamination or foaming.
  

Operator Anecdotes and Field Cases

• Operators in forestry have reported intermittent grapple issues when using older 873F models with high-hour auxiliary pumps. Cleaning solenoids and replacing worn hoses often restored full functionality.
  
• Construction sites using augers noted slower operation when hydraulic fluid temperature exceeded 180°F, highlighting the importance of fluid quality and heat management.
  

Engineering Notes and Technical Data

• Pump specifications: Standard flow 23 GPM, high-flow 32 GPM
  
• Pressure rating: 3,000 psi maximum
  
• Solenoid voltage: 12V nominal, tolerance ±1V
  
• Hydraulic fluid: Caterpillar HYDO Advanced, ISO VG 46
  

Advanced Troubleshooting

• Use diagnostic software or handheld meters to check for solenoid response time.
  
• Measure actual flow at the attachment to identify pressure drops.
  
• Inspect internal valve spools for wear or pitting.
  

Preventive Measures and Upgrades

• High-flow auxiliary kits can enhance performance for heavy-duty attachments.
  
• Protective covers and routing clamps reduce hose wear.
  
• Electrical diagnostic tools help prevent solenoid failures.
  

Case Studies

• In a landscaping company, retrofitting an older 873F with new solenoids and hydraulic hoses increased attachment response time by 25%.
  
• In a logging operation, using the correct hydraulic fluid and maintaining optimal temperature reduced grapple stalling by 40%.
  

Conclusion
Auxiliary hydraulic issues on the Caterpillar 873F skid steer require a systematic approach to diagnosis. By understanding the electrical and hydraulic components, monitoring fluid condition, and performing preventive maintenance, operators can ensure reliable operation. High-flow auxiliary kits, careful attachment selection, and regular system checks significantly enhance productivity and reduce downtime.