Replacing the Hydraulic Line from Filter to Pump on a Bobcat 773 Skid Steer

[MikePhua]

The Bobcat 773 and Its Hydraulic System Layout
The Bobcat 773 skid steer loader, part of the C-Series lineup, was designed for compact performance with a robust hydrostatic drive system. Manufactured in the late 1990s and early 2000s, the 773 became a staple in landscaping, construction, and agricultural operations. Its hydraulic architecture includes a hydrostatic filter mounted near the engine compartment, with fluid routed through a series of hoses to the pump, cooler, and reservoir.
One critical hose connects the right side of the hydrostatic filter to the pump or reservoir area. This line plays a key role in maintaining fluid flow and pressure balance within the hydrostatic loop. Over time, due to heat, vibration, and age, this hose can develop leaks or fail entirely—requiring replacement to restore system integrity.
Terminology:

• Hydrostatic drive: A propulsion system using hydraulic fluid to power wheel motors via variable displacement pumps
  
• JIC fitting: Joint Industry Council standard hydraulic fitting, typically 37° flare, used for high-pressure connections
  
• Case drain: A low-pressure return line that relieves excess fluid from motor housings to the reservoir
  

Identifying the Hose and Its Specifications
The hose in question is approximately 32 inches long with straight female JIC connectors on both ends. It connects the right side of the hydrostatic filter to a component mounted above the hydraulic tank—likely the pump or a return manifold. In Bobcat’s parts catalog, this hose is listed as item #17 with part number 6704159, though variations may exist depending on whether the machine originally had a hard line in place.
Operators should verify the fitting type and hose routing before ordering replacements. In some cases, previous owners may have modified the system, replacing hard lines with flexible hoses for ease of maintenance.
Recommended specs:

• Hose type: Parker 206-6 or equivalent
  
• Fittings: Female JIC, straight
  
• Length: 32 inches (±⅛ inch tolerance)
  
• Protective sleeve: Optional cloth wrap to prevent abrasion and UV damage
  

Challenges in Hose Replacement and Shop Limitations
Local hydraulic shops may struggle to match exact hose lengths, often citing manufacturing tolerances. While a deviation of ⅛ inch is generally acceptable, anything beyond that can complicate installation—especially in tight compartments like the Bobcat 773’s engine bay.
Tips for accurate hose fabrication:

• Measure from fitting seat to fitting seat, not overall length
  
• Use a flexible tape and mark routing path before removal
  
• Request protective sleeves for hoses routed near hot surfaces or sharp edges
  
• Confirm pressure rating and temperature tolerance for hydrostatic applications
  

One operator recalled a shop producing a hose an inch too short, leading to a frustrating installation deep within a skidder’s frame. Precision matters, especially when elbows and bulkhead fittings are involved.
Field Repair Options and DIY Solutions
For those preferring to avoid the shop altogether, field-attachable fittings and bulk hose can be ordered online. With basic tools and careful measurement, operators can build their own replacement hoses using Parker-style reusable fittings.
DIY approach:

• Order Parker 206-6 hose in bulk
  
• Use field-attachable JIC fittings with proper crimp or compression tools
  
• Test for leaks using low-pressure startup before full operation
  
• Document hose specs for future replacements
  

This method eliminates delays and ensures full control over hose quality and fitment. It’s especially useful for remote operators or those managing older fleets with discontinued parts.
Hydraulic Cleanliness and System Refill
After replacing the hose, it’s essential to maintain hydraulic cleanliness. Contaminants introduced during hose removal can damage pumps and valves. Use lint-free cloths, cap open fittings, and flush the system if contamination is suspected.
Fluid recommendations:

• Bobcat hydraulic fluid or ISO 46 equivalent
  
• Filter replacement during hose change
  
• Bleed air from system by cycling controls gently
  
• Monitor fluid level and temperature during initial run
  

Hydraulic cleanliness is governed by ISO 4406 standards, which quantify particle contamination. While most operators don’t measure this directly, using clean tools and proper fluid handling can prevent costly failures.
Conclusion
Replacing the hydraulic line from the filter to the pump on a Bobcat 773 is a straightforward but precision-sensitive task. Whether sourcing OEM parts or fabricating a custom hose, attention to length, fitting type, and cleanliness ensures reliable performance. In compact loaders, every hose carries the weight of the machine’s motion—and getting it right means keeping the job moving without a hitch.