Adapting Dozer Hydraulic Lines for Use with a Bobcat Skid Steer: A Practical Engineering Approach

[MikePhua]

Understanding the Challenge
Repurposing or adapting heavy machinery often means finding ways to bridge the gap between different eras, manufacturers, and hydraulic systems. One common modern challenge is how to connect the hydraulic lines of a dozer blade—typically designed for older tractors or crawler equipment—to the auxiliary hydraulics of a modern Bobcat skid steer. This can open up cost-saving possibilities by reusing older attachments for grading, clearing, or land contouring without investing in new specialized tools.
However, the task isn’t as simple as just connecting hoses. It involves understanding flow rates, return paths, hydraulic quick coupler styles, valve behavior, and safety considerations. What seems like a simple plumbing job can quickly spiral into a lesson in hydraulic engineering if not planned properly.
Hydraulic Basics: Pressure, Flow, and Return
Before diving into fittings and couplers, one must understand the core components of hydraulic logic:

• Pressure Line (Supply): This is the line that delivers high-pressure hydraulic fluid from the skid steer to the attachment. It powers movement (e.g., raising or angling the blade).
  
• Return Line: This allows fluid to flow back from the attachment to the machine’s reservoir.
  
• Case Drain (if needed): On high-flow or motor-based attachments, a third, low-pressure line helps relieve excess pressure buildup in motor housings.
  

Bobcat skid steers typically have two quick-connect hydraulic ports at the front—one for pressure, one for return. Dozer blade hydraulic setups, particularly on older blades used with crawler tractors, might use more basic connections or even open-center systems that continuously circulate fluid.
Identifying System Compatibility
To safely and effectively connect a dozer blade’s hydraulic cylinders to a Bobcat skid steer, several compatibility factors must be considered:

• Hydraulic pressure range: Most Bobcat machines operate at pressures of 3,000 to 3,500 PSI. Older dozer hydraulics may have been rated lower. Check both specs.
  
• Flow rate: High flow can blow seals on small bore cylinders if the attachment isn’t designed for it.
  
• Valve control type: A dozer blade may be controlled via manual spool valves, while the Bobcat uses electric or joystick-based actuators.
  
• Quick coupler types: Bobcat standard couplers are flat-face ISO 16028; the dozer blade may have JIC, ORB, or NPT-threaded ports.
  

Steps to Hook Up a Dozer Blade to a Skid Steer

1. Inspect the Blade's Cylinders
   Determine the number and type of hydraulic cylinders. Most dozer blades use:
   • Two angle cylinders to shift the blade left or right.
     
   • Optionally, a tilt cylinder for slope control.
     
2. Map the Hydraulic Ports
   Locate the inlets and outlets of each cylinder. On some setups, lines may already be attached. Trace where each hose leads and confirm direction of travel when pressurized.
   
3. Install or Replace Hydraulic Hoses
   Use appropriate hoses rated for at least 3,500 PSI working pressure. Hoses should:
   • Be long enough to accommodate full movement of the blade and machine arms.
     
   • Be protected from pinching or rubbing (use abrasion sleeves).
     
4. Attach Hydraulic Couplers
   Replace the dozer's existing couplers with flat-face quick couplers to match the Bobcat's system. Adapters may be required:
   • From NPT or JIC to flat-face ISO.
     
   • Always use Teflon tape or hydraulic sealant on tapered thread fittings.
     
5. Connect to the Skid Steer
   With the skid steer off and depressurized:
   • Wipe coupler ends clean.
     
   • Connect pressure and return lines to the appropriate ports.
     
   • Be sure not to reverse them—reversed lines can dead-head the pump or damage valves.
     
6. Test at Low Flow
   Start the skid steer and gently engage hydraulic flow. Watch the cylinders move. If the blade reacts too quickly or jerks:
   • Use a flow restrictor or needle valve to slow the response.
     
   • Consider adjusting the control settings in the skid steer, if available.
     
7. Secure Lines and Test Movement Range
   Fully extend and retract the cylinders, watching for:
   • Hose rubbing or snagging.
     
   • Binding or sticking.
     
   • Cylinder rod leakage.
     

Common Pitfalls and Solutions

• Hoses “locking up” after shutdown: This happens when pressure remains trapped in the lines. The fix:
  • Install quick couplers with pressure relief buttons.
    
  • Or crack a fitting to relieve pressure before disconnecting.
    
• Blade cylinders creeping or drifting: Indicates internal bypass or mismatched flow. Check:
  • Cylinder seals.
    
  • Return flow path (must not be blocked).
    
  • That the skid steer isn’t in “float” mode unintentionally.
    
• Skid steer bogging under blade load: The blade may be too heavy or hydraulic flow insufficient. Solutions:
  • Add counterweights.
    
  • Avoid full downforce; let the blade float slightly.
    

Real-World Story: A Farmer’s Fix in North Dakota
In 2014, a farmer in eastern North Dakota repurposed an old International dozer blade to clear shelterbelts with his Bobcat S185. The original blade had two ancient single-acting cylinders with leaky seals. Rather than scrapping them, he converted them to double-acting by adding return ports, replaced all hoses with modern Parker fittings, and used a flow restrictor to keep the movements smooth. He ended up grading 15 miles of ditch berms using the hybrid machine—something local contractors quoted at $12,000.
Adding Electric Solenoids for Multiple Functions
For those wanting to control multiple hydraulic functions (e.g., tilt and angle) from a single pair of skid steer lines, electric selector valves can be installed. These are small 12V solenoid-controlled diverter valves that allow the operator to switch flow from one cylinder pair to another with a button.
Parts needed include:

• 12V solenoid valve block (usually 6-port, 2-position).
  
• Electrical toggle switch in the cab.
  
• Wiring harness and inline fuse.
  
• Mounting bracket near the attachment.
  

This system is particularly useful for running complex attachments without adding expensive auxiliary ports to the skid steer.
Safety Considerations

• Always depressurize hydraulics before disconnecting.
  
• Never stand in the line of hydraulic spray—pin-hole leaks can inject fluid under the skin, requiring emergency surgery.
  
• Check fluid temperatures—hot hydraulic oil can cause burns.
  
• Never dead-head a hydraulic line (no return path), which can destroy pumps or burst hoses.
  

Conclusion: Mechanical Ingenuity Meets Practical Application
Adapting a dozer blade to a Bobcat skid steer requires more than fittings and hoses—it demands an understanding of hydraulic behavior, machine limits, and practical engineering. With care and planning, older attachments can be brought back to life and paired with modern machines for cost-effective performance in land clearing, snow pushing, or grading applications.
As technology evolves, these kinds of hybrid solutions keep machinery relevant, efficient, and affordable—honoring both old-school craftsmanship and new-world adaptability.