Restoring and Operating the 1970 International H-25 Pay Loader

[MikePhua]

The H-25’s Place in International Harvester’s Equipment Line
The International H-25 pay loader was part of a broader push by International Harvester in the 1960s and early 1970s to expand its presence in the construction equipment market. Known primarily for its agricultural tractors and trucks, IH began producing wheel loaders to compete with Caterpillar, Michigan, and Allis-Chalmers in the mid-sized loader segment. The H-25 was designed as a rugged, mechanically simple machine with a rated bucket capacity of approximately 2.5 cubic yards and an operating weight near 20,000 lbs.
Powered by an inline-six gasoline or diesel engine—depending on configuration—the H-25 featured a torque converter transmission, hydraulic steering, and a robust planetary final drive system. Though not as refined as later hydrostatic models, the H-25 earned a reputation for reliability and ease of service, especially in rural and industrial settings where dealer support was limited.
Initial Inspection and Startup Checklist
Before putting an H-25 back into service, especially one that has sat idle or been recently acquired, a thorough inspection is essential. Key areas to check include:

• Engine oil level and condition
  
• Hydraulic fluid reservoir and filter
  
• Transmission fluid (typically Type A or Dexron II)
  
• Coolant level and radiator integrity
  
• Brake fluid and pedal response
  
• Tire pressure and sidewall condition (if pneumatic tires are fitted)
  
• Grease points on loader arms, bucket pivots, and steering knuckles
  

It’s also wise to inspect the battery, starter solenoid, and ignition wiring. Many older H-25s used mechanical voltage regulators, which can fail silently and cause charging issues. Replacing with a modern solid-state regulator is a common upgrade.
Power Steering Troubleshooting
One of the most common issues reported with the H-25 is non-functional power steering. The system is hydraulically assisted and relies on a dedicated pump driven off the engine accessory belt. If the steering becomes stiff or unresponsive, possible causes include:

• Low hydraulic fluid in the steering reservoir
  
• Air in the hydraulic lines
  
• Worn or leaking steering cylinder seals
  
• Failed steering pump or clogged inlet screen
  
• Broken or slipping drive belt
  

To diagnose, start by checking fluid level and condition. If the fluid is milky, water contamination may be present. Bleed the system by cycling the steering lock-to-lock several times with the engine running. If no improvement is seen, remove the pump and inspect the internal vanes or gears for wear.
In one restoration case, a technician discovered that the steering pump inlet hose had collapsed internally, restricting flow. Replacing the hose restored full steering function without needing to rebuild the pump.
Hydraulic System Maintenance and Upgrades
The H-25’s loader arms and bucket are powered by a gear-type hydraulic pump mounted near the engine. The system uses open-center hydraulics, meaning fluid constantly circulates until a valve is actuated. Over time, seals in the control valve and cylinders may degrade, leading to slow response or drift.
Recommended maintenance includes:

• Replacing hydraulic filters every 250 hours
  
• Flushing the system with clean fluid every 1,000 hours
  
• Inspecting hoses for abrasion and cracking
  
• Repacking lift and tilt cylinders with new seals
  

Some owners have upgraded the control valve to a modern joystick-style unit, improving ergonomics and reducing operator fatigue. This requires adapting the hose fittings and mounting brackets but can be done with basic fabrication tools.
Electrical System and Instrument Panel Considerations
The original instrument panel on the H-25 includes basic gauges: oil pressure, coolant temperature, ammeter, and fuel level. These are often faded, non-functional, or missing entirely. Replacing them with aftermarket 2-inch gauges is straightforward and improves reliability.
Wiring harnesses on older machines tend to suffer from brittle insulation and corroded terminals. A full rewire using marine-grade wire and sealed connectors is recommended for long-term reliability. Adding a fuse block and master disconnect switch can prevent electrical fires and simplify troubleshooting.
Stories from the Field
A cabinetmaker in Ontario acquired a 1970 H-25 for snow removal and yard cleanup. After replacing the battery and cleaning the carburetor, the machine started easily but had no steering assist. He traced the issue to a dry steering pump and added fluid—restoring function instantly. Later, he fabricated a custom canopy using salvaged steel tubing and added LED work lights for winter operation.
In another case, a rural municipality in Iowa used an H-25 for gravel road maintenance. After 40 years of service, the loader was retired and donated to a vocational school, where students rebuilt the engine and hydraulic system as part of a hands-on training program.
Conclusion
The International H-25 pay loader may be over half a century old, but its mechanical simplicity and robust design make it a viable machine for restoration and light-duty work. With attention to hydraulic, electrical, and steering systems, owners can bring these loaders back to life and enjoy the satisfaction of operating a piece of American industrial history. Whether clearing snow, moving gravel, or grading a driveway, the H-25 proves that old iron still has plenty of muscle left.