Hydraulic Priority and Flow Disruption in the ASV RC-100 Track Loader

[MikePhua]

The RC-100 and Its High-Flow Hydraulic System
The ASV RC-100, introduced in the mid-2000s, was designed as a high-performance compact track loader capable of powering demanding attachments like forestry mulchers, stump grinders, and brush cutters. With a 100 hp Perkins diesel engine and a hydraulic system delivering up to 40 gpm at 3,000 psi, the RC-100 was one of the most powerful machines in its class. ASV, founded in Minnesota in 1983, built its reputation on rubber track technology and specialized forestry equipment. The RC-100 became a favorite among land-clearing contractors and utility crews for its stability, hydraulic output, and rugged undercarriage.
The machine features dual hydraulic circuits: a high-flow auxiliary system for demanding attachments and a low-flow circuit for standard tools. These circuits are managed by a priority valve system that allocates flow based on operator input and system demand. When attachments stall or overload, the hydraulic priority logic can interrupt other functions, including lift and tilt.
Terminology Annotation
- Hydraulic Priority Valve: A control valve that directs flow to critical functions based on pressure and demand, often favoring auxiliary circuits during operation.
- Dead Stall: A condition where an attachment stops rotating due to excessive load, causing hydraulic pressure to spike and flow to halt.
- Quick Disconnects: Couplers that allow fast connection and disconnection of hydraulic lines, typically used for attachments.
- Spool Valve: A sliding valve element inside a hydraulic control block that directs fluid to actuators based on joystick input.
Symptoms of Flow Interruption During Attachment Use
Operators may observe that when using high-demand attachments like a FAE mulcher, the loader arms refuse to lift if the attachment stalls. Similarly, when using low-flow tools such as tire grapplers, holding the cylinder extension button can prevent the loader from responding. These symptoms suggest that the hydraulic priority system is diverting all available flow to the auxiliary circuit, leaving the lift and tilt functions starved.
Key indicators include:

• Loader arms remain inactive during attachment stall
  
• Hydraulic fluid temperature rises rapidly under load
  
• Lift resumes only after attachment spools down
  
• No fault codes or warning lights appear
  
• Same attachment behaves normally on other RC-100 units
  

This behavior points to a configuration or valve logic issue rather than a mechanical failure.
A Story from the Pacific Northwest
In Washington State, a land-clearing contractor purchased a used 2006 RC-100 to run a FAE mulcher. During operation, he noticed that when the mulcher stalled in dense brush, the loader arms would not lift until the head regained speed. Suspecting a relief valve issue, he traced the hydraulic lines and discovered that the high-flow circuit was upstream of the boom control valve. The priority valve was locking out the lift function during pressure spikes. After consulting a hydraulic technician, he installed a flow divider and adjusted the relief settings to balance flow between circuits. The issue was resolved, and the machine performed reliably under full load.
Root Causes and Diagnostic Strategy
Several factors can contribute to hydraulic flow interruption:

• Priority valve configuration favoring auxiliary circuit
  
• Relief valve set too low on the boom control block
  
• Spool valve sticking due to contamination or wear
  
• Hydraulic pump unable to maintain flow under dual demand
  
• Quick disconnects restricting flow due to internal damage
  

To diagnose:

• Check hydraulic pressure at the auxiliary and lift circuits during operation
  
• Inspect priority valve for adjustment screws or shims
  
• Test relief valve settings with a calibrated gauge
  
• Clean or replace spool valves if sticking is suspected
  
• Compare performance with identical RC-100 units under similar load
  

If the issue persists, consider installing a manual override or secondary flow control valve to ensure lift function remains active during attachment stall.
Recommendations for Repair and Optimization
To improve hydraulic performance:

• Adjust priority valve to allow partial flow to lift circuit during auxiliary demand
  
• Replace quick couplers with high-flow rated units to reduce restriction
  
• Install a flow divider to balance output between circuits
  
• Upgrade hydraulic pump if wear is detected or output is below spec
  
• Flush system and replace filters to remove contamination
  

For forestry applications, consider adding a hydraulic cooler to manage fluid temperature and prevent viscosity breakdown under sustained load.
Conclusion
The ASV RC-100’s hydraulic system is powerful but sensitive to flow prioritization, especially when running high-demand attachments. When auxiliary tools stall, the priority valve may starve other functions, leading to temporary loss of lift or tilt. By understanding the system layout and adjusting valve settings, operators can restore balanced performance and maintain control during peak load conditions. With proper tuning and preventative care, the RC-100 remains a formidable tool in land-clearing and heavy-duty attachment work.