Comprehensive Guide to the ASV 4520HD Compact Track Loader: Features, Common Issues, and Practical Maintenance Insights

[MikePhua]

Introduction to the ASV 4520HD
The ASV 4520HD is a powerful, durable compact track loader designed for demanding construction, landscaping, and agricultural tasks. Featuring a robust build and a high-performance John Deere engine, the 4520HD delivers reliable operation in varied terrains, particularly excelling in environments requiring low ground pressure and high traction.
This comprehensive guide covers the machine’s technical specifications, common operational and hydraulic issues reported by users, maintenance advice, troubleshooting steps, and practical solutions. Supplementing the technical content is terminology explanation and illustrative case insights to assist operators, mechanics, and fleet owners in maximizing the performance and longevity of the ASV 4520HD.

Technical Specifications and Features

• Engine:
  • John Deere 4045T Diesel turbocharged engine rated at approximately 115 horsepower.
    
  • Known for fuel efficiency and dependable power delivery suited for heavy-duty loader functions.
    
• Hydraulic System:
  • Standard low flow auxiliary hydraulic system delivers about 19 gallons per minute (GPM) at 3,000 psi.
    
  • High flow option provides up to 30 GPM at 3,000 psi, enabling operation of power-demanding attachments.
    
  • The hydraulic system supports loader lift, bucket curl, power take-off (PTO), and auxiliary functions via tandem gear pumps.
    
• Operating Weight and Capacity:
  • Operating weight near 8,500 lbs, providing good machine stability and traction.
    
  • Rated operating capacity about 2,837 lbs at 50% tipping load, fitting mid-range lift needs.
    
  • Ground pressure around 2.65 psi thanks to 18-inch wide rubber tracks enhancing flotation and maneuverability.
    
• Lift Design and Clearance:
  • Radial lift design maximizes reach and loading height, beneficial for material placement and truck loading.
    
  • Higher ground clearance (approximately 16 inches) than many competitors improves capability in rough terrain.
    
• Transmission:
  • Features a single-speed hydrostatic drive transmission providing reliable track movement and controlled speed.
    

Common Operational Issues and Diagnostics

• Loss of Auxiliary and PTO Functions:
  Users report sudden loss of auxiliary hydraulic power and PTO operation, while loader lift and bucket curl remain functional. This often indicates an issue within the tandem gear pump assembly, particularly in the front section supplying the auxiliary and PTO functions.
  
• Tandem Gear Pump Failure:
  Internal gear components may become damaged or sheared, causing loss of flow and hydraulic pressure to auxiliary circuits. The rear gear section typically powers loader lift and curl, so its functionality is retained even when the front section fails.
  
• Hydraulic Suction Strainer Blockage:
  Plugged suction strainers can cause low pump inlet pressure, leading to poor hydraulic pump function and failure symptoms. Regular strainer and filter maintenance is critical.
  
• Relief Valve or Selector Valve Faults:
  Defective relief valves in the PTO/auxiliary selector valve can restrict flow or cause incorrect pressure settings, generating function loss or erratic behavior.
  
• Transmission and Track Performance Issues:
  After transmission replacement, operators have observed track slowdown, particularly on one side, and loss of turning capability when hydraulic systems heat up during operation. Causes may include charge pressure issues, failed relief or crossover valves, worn drive motors or pumps, or faulty parking brake pressure circuits.
  

Detailed Troubleshooting Steps

• Hydraulic Flow Check:
  • Remove outlet lines from the tandem gear pump front section, run the engine briefly to test flow into a clean container.
    
  • Absence or low flow indicates pump damage or blockage.
    
• Visual Inspection of Pump Components:
  • Disassemble the tandem gear pump to inspect gears for wear, breakage, or sheared keys.
    
  • Replace damaged internal components promptly to prevent further failure.
    
• Inspect Hydraulic Filters and Suction Strainers:
  • Clean or replace hydraulic suction strainers regularly to maintain flow quality.
    
  • Change hydraulic filters per manufacturer recommendations to avoid contamination buildup.
    
• Check Relief and Selector Valves:
  • Test auxiliary and PTO relief valves for correct pressure setting and operation.
    
  • Inspect PTO/auxiliary selector valves for internal leaks or valve sticking.
    
• Transmission and Drive System Diagnostics:
  • Monitor hydraulic oil temperature; over 160°F (71°C) indicates overheating, causing hydraulic fluid thinning and flow loss.
    
  • Measure charge and drive pressures on both tracks cold and hot, comparing against specifications.
    
  • Examine parking brake function to rule out partial engagement causing track resistance.
    
  • Confirm absence of worn drive motors or pumps causing reduced track power.
    

Terminology Clarification

• Auxiliary Hydraulic Function: Output flow from a loader’s hydraulic system used to power attachments such as mowers, augers, or grapples.
  
• Power Take-Off (PTO): A mechanical or hydraulic function that drives external implements from the machine’s power source.
  
• Tandem Gear Pump: A hydraulic pump composed of two gear sections operating in series or parallel to provide multiple hydraulic circuits.
  
• Suction Strainer: A filter located at the pump inlet preventing large contaminants from entering the pump.
  
• Relief Valve: Hydraulic valve that limits system pressure to safe levels by diverting excess flow.
  
• Selector Valve: Valve that directs hydraulic flow to different circuit branches based on function selection.
  
• Charge Pressure: Hydraulic pressure used to maintain pump and motor operation in track drives.
  
• Cross-Over Relief Valve: Valve that balances hydraulic flow between track drive circuits.
  

Practical Maintenance Advice and Solutions

• Regular Inspection and Maintenance of Hydraulic Gear Pumps:
  • Schedule pump inspections to detect gear wear or breakage early.
    
  • Replace the tandem gear pump or internal sections if damage is confirmed.
    
  • Source quality replacement parts from trusted suppliers to ensure longevity.
    
• Maintain Clean Hydraulic Fluid and Filtration Systems:
  • Follow strict filter replacement schedules.
    
  • Clean hydraulic tanks and suction strainers routinely to avoid contamination-induced failures.
    
• Monitor Hydraulic Temperature:
  • Avoid extended operation at excessive temperatures.
    
  • Use hydraulic oil coolers or supplemental cooling if the machine operates frequently in high-heat environments.
    
• Transmission and Track System Care:
  • Test pressures after transmission service or replacement.
    
  • Inspect relief valves and parking brake circuits for proper function.
    
  • Check for worn drive motors or pumps and replace as necessary.
    
• Advance Diagnostic Tools Usage:
  • Utilize pressure gauges and flow meters when diagnosing hydraulic and drive issues.
    
  • Employ manufacturer service manuals and schematics for accurate pressure values and system diagrams.
    

Case Story: Overcoming Tandem Pump Failure and Track Issue on ASV 4520HD
An ASV 4520HD operator encountered sudden loss of auxiliary and PTO hydraulic functions while mower attachment lift and curl operations remained unaffected. Inspection revealed that the front section of the tandem gear pump, which powers auxiliary circuits, had suffered internal gear damage with sheared pieces.
After removing the pump, complete teardown showed the gears fragmented inside. Replacement parts were sourced from specialized hydraulic service centers to rebuild the pump at significantly less cost than a full new unit.
Subsequently, the same machine exhibited track slowdown and loss of turning ability after transmission replacement. By monitoring hydraulic temperatures and pressures, the technician identified an issue with the crossover relief valve and a partial parking brake application. After valve replacements and adjustments combined with a hydraulic oil change, steering responsiveness and track performance returned to normal.
This case highlights the importance of comprehensive hydraulic system knowledge, regular maintenance, and systematic diagnostics to sustain ASV 4520HD productivity.

Summary List of Key Points and Recommendations

• ASV 4520HD is equipped with a 115 hp John Deere 4045T engine and a tandem gear pump providing separate hydraulic circuits.
  
• Auxiliary and PTO functions rely on the front section of the tandem gear pump; loader lift and curl depend on the rear section.
  
• Gear pump internal failure can cause complete loss of auxiliary/PTO flow while loader functions remain intact.
  
• Hydraulic strainers and filters play a critical role in preventing pump contamination and failures.
  
• Transmission overheating, worn drive motors, relief valve faults, and parking brake issues can cause track slowdown and steering problems.
  
• Use pressure and flow testing tools to diagnose hydraulic and drive system problems accurately.
  
• Source quality parts for pump repairs or replacements to extend system reliability.
  
• Perform routine hydraulic fluid changes and temperature monitoring to safeguard pump and transmission health.
  
• Follow manufacturer maintenance manuals and service intervals diligently.
  

Additional Practical Tips

• Keep spare suction strainers and hydraulic filters on hand for regular replacement.
  
• Train operators to recognize symptoms of hydraulic failures such as loss of auxiliary function or track power loss.
  
• Maintain clear maintenance logs documenting repairs, parts replaced, and system performance trends.
  
• Consider installing hydraulic temperature sensors and gauges if not factory-equipped for proactive monitoring.
  
• Consult manufacturer technical support or specialized repair shops for complex hydraulic pump or transmission repairs.
  

Conclusion
The ASV 4520HD compact track loader is a versatile machine with complex hydraulic and drive systems. Failures in the tandem gear pump’s front section commonly result in loss of auxiliary and PTO functions, while the loader lift functions rely on the rear pump section. Additionally, transmission and track drive issues such as track slowdown or loss of turning often stem from hydraulic system problems, worn components, or valve faults.
Thorough diagnostic procedures, regular hydraulic maintenance, clean filtration, and timely repairs extend the machine’s operational life and reliability. Real-world cases illustrate the critical nature of understanding the interplay between hydraulic circuits, pump internals, and transmission components.
This detailed guide combines specifications, terminology, troubleshooting workflows, maintenance advice, and case experiences to equip owners, technicians, and operators in managing the ASV 4520HD effectively for sustained productivity and minimized downtime.