Restoring the Case 680C Construction King Backhoe

[MikePhua]

The Case 680C and Its Role in Construction History
The Case 680C Construction King was introduced in the mid-1970s by J.I. Case Company, a manufacturer with roots dating back to 1842. Known for its rugged agricultural and construction machinery, Case launched the Construction King series to compete with Ford and John Deere in the growing backhoe-loader market. The 680C was a mid-sized model featuring a mechanical shuttle transmission, a robust diesel engine, and a fully integrated loader-backhoe design.
With a digging depth of over 14 feet and a loader lift capacity exceeding 5,000 lbs, the 680C was widely adopted by municipalities, contractors, and utility crews. By the early 1980s, Case had sold tens of thousands of units across North America, and many remain in service today—often as restoration projects or farmyard workhorses.
Air Brake System and Compressor Challenges
One of the more complex systems on the 680C is its air brake setup, which includes an engine-driven compressor, brake chambers, and an air governor. After decades of use, these components often suffer from oil contamination, diaphragm failure, or pressure loss.
Common issues:

• Oil in air lines due to worn compressor seals
  
• Inability to maintain 125 psi due to leaks or faulty governor
  
• Brake chamber bladder rupture from age or overpressure
  
• Missing or corroded air tanks and fittings
  

Terminology:

• Air Governor: A pressure-regulating valve that controls when the compressor engages or unloads.
  
• Brake Chamber: A pressurized canister that converts air pressure into mechanical force to apply brakes.
  

A retired electrician in Virginia revived his 680C after a decade of dormancy. He sourced a Bendix-style air governor and a standard Type 24 brake chamber from a local truck parts supplier, restoring brake function for under $100.
Safety Hazards in Brake Chamber Servicing
Servicing brake chambers requires extreme caution. Inside the spring brake portion is a powerful coil spring that can eject with lethal force if disassembled improperly. Technicians must use a certified cage or purchase pre-assembled units.
Safety recommendations:

• Never open a spring brake chamber unless it’s caged
  
• Replace entire chamber rather than rebuild
  
• Use eye protection and follow OSHA guidelines
  
• Confirm rod length and clevis compatibility before installation
  

Terminology:

• Spring Brake: A fail-safe brake that engages when air pressure is lost, using a powerful internal spring.
  
• Clevis: A U-shaped connector that attaches the brake rod to the linkage.
  

In 2021, a mechanic in Ohio suffered a hand injury while attempting to disassemble a chamber without proper tools. The incident led to a statewide training update for municipal fleet technicians.
Hydraulic Hose Replacement and Pump Rebuild
The hydraulic system on the 680C includes a front-mounted pump beneath the engine, feeding fluid to the loader and backhoe circuits. After years of sitting idle, hoses often crack, and O-rings degrade. Replacing these components is essential before pressurizing the system.
Steps for hydraulic restoration:

• Identify hose lengths and fitting types
  
• Use Parker or Aeroquip hoses for durability
  
• Replace all O-rings with Viton or Buna-N rated for hydraulic fluid
  
• Flush system with clean fluid before startup
  

Terminology:

• O-Ring: A circular gasket used to seal joints in hydraulic systems.
  
• Hydraulic Shop: A facility that fabricates custom hoses and fittings for fluid power systems.
  

A technician in Pennsylvania rebuilt a 680C hydraulic pump using a kit sourced from a vintage parts dealer. He emphasized avoiding low-quality hoses, noting that Chinese imports failed within 300 hours of use.
Parts Sourcing and Aftermarket Solutions
Finding parts for a 45-year-old machine can be daunting. While Case no longer supports the 680C directly, many components are shared with later models or available through aftermarket suppliers. Key strategies include:

• Salvage yards specializing in vintage Case equipment
  
• Online catalogs from independent parts dealers
  
• Cross-referencing part numbers with truck industry equivalents
  
• Fabricating brackets or plates when OEM parts are discontinued
  

Terminology:

• Aftermarket Part: A non-OEM component designed to fit and function like the original.
  
• Cross-Reference: Matching a part number to equivalent items from other manufacturers.
  

In 2023, a restoration shop in North Carolina began offering refurbished air compressors for older Case machines, citing demand from hobbyists and small contractors.
A Machine Worth Saving
The Case 680C may not have the electronics or comfort of modern loaders, but its mechanical simplicity and robust design make it a favorite among those who value hands-on restoration. Whether it’s replacing brake chambers, rebuilding hydraulic pumps, or sourcing an elusive air governor, the process is as much about preserving history as it is about utility.
Maintenance tips:

• Grease all pivot points monthly
  
• Change engine oil every 100 hours
  
• Inspect air system for leaks quarterly
  
• Replace hydraulic filters every 500 hours
  

A retired operator in Georgia summed it up best: “The 680C isn’t just a backhoe—it’s a reminder of when machines were built to last, and fixing them was part of the job.”
Conclusion
Restoring a Case 680C Construction King is a journey through time and torque. With patience, resourcefulness, and respect for its design, this classic backhoe can return to work with dignity. Whether you're sourcing brake parts from a truck shop or fabricating a new floor plate, every fix is a tribute to the machine’s enduring legacy. In the world of heavy equipment, some kings never abdicate—they just need a little help getting back on the throne.