LeRoi Air Compressors Mechanical Heritage and Restoration Challenges

[MikePhua]

The LeRoi Brand and Its Industrial Legacy
LeRoi air compressors trace their roots back to the early 20th century, when the LeRoi Company—originally founded in Milwaukee—began producing industrial-grade machinery for mining, construction, and energy sectors. Known for their robust cast-iron construction and straightforward mechanical design, LeRoi compressors became a staple in remote operations where reliability mattered more than refinement. By the mid-1900s, LeRoi had expanded its product line to include rotary screw and reciprocating compressors, many of which were trailer-mounted and powered by gasoline or diesel engines.
Though the company changed ownership multiple times—eventually becoming part of CompAir and later Gardner Denver—the original LeRoi units still circulate in the field, especially in rural workshops, legacy fleets, and restoration circles. Their mechanical simplicity makes them ideal candidates for rebuilds, but sourcing parts and documentation can be a challenge.
Terminology Clarification

• Reciprocating compressor: A piston-driven air compressor that uses crankshaft motion to compress air in cylinders.
  
• Rotary screw compressor: A continuous-duty compressor that uses interlocking helical screws to compress air.
  
• Unloader valve: A device that releases pressure from the compressor head during startup to reduce load.
  
• Aftercooler: A heat exchanger that cools compressed air before it enters the tank or system.
  

Common Issues in Legacy LeRoi Units
Owners of older LeRoi compressors often encounter:

• Hard starting due to worn ignition systems or fuel delivery issues
  
• Oil leaks from aged seals and gaskets
  
• Low compression from worn piston rings or valves
  
• Electrical faults in starter motors or control panels
  
• Air delivery inconsistencies caused by clogged filters or malfunctioning unloaders
  

A technician in Alberta restored a 1970s LeRoi portable unit and found that the original magneto ignition had degraded. After retrofitting a modern coil and replacing the carburetor, the unit started reliably and delivered consistent pressure.
Restoration Strategy and Parts Sourcing
Restoring a LeRoi compressor requires patience and resourcefulness. Key steps include:

• Identifying the model and serial number, often stamped on the crankcase or frame
  
• Locating a parts manual or service bulletin through vintage equipment forums or archives
  
• Disassembling the compressor head and inspecting cylinder walls, valves, and pistons
  
• Replacing all gaskets, seals, and filters with compatible aftermarket equivalents
  
• Rewiring the control panel and testing safety switches and pressure sensors
  

Recommended components:

• SAE-rated compressor oil with anti-foaming additives
  
• Copper or braided steel lines for high-pressure connections
  
• Inline moisture traps and pressure regulators for system protection
  
• Modern air filters with equivalent flow ratings
  

A contractor in Georgia rebuilt a LeRoi 125CFM unit and used a mix of NOS parts and custom-machined valve plates. The machine was later used to power pneumatic tools during a barn restoration project.
Operational Tips and Preventive Maintenance
To keep a restored LeRoi compressor running smoothly:

• Warm up the engine before engaging full load
  
• Drain moisture from the tank daily to prevent corrosion
  
• Monitor oil level and change every 250 hours or seasonally
  
• Inspect belts and pulleys monthly for wear or misalignment
  
• Test safety valves and pressure cutoffs quarterly
  

Operator tips:

• Avoid running the compressor at max RPM for extended periods
  
• Use a tachometer to verify engine speed under load
  
• Install a temperature gauge on the head to monitor overheating
  
• Store the unit indoors or under cover to protect electrical components
  

A crew in British Columbia added a digital hour meter and temperature sensor to their LeRoi unit, allowing them to track service intervals and prevent thermal damage during summer operation.
Modern Alternatives and Retrofit Possibilities
While LeRoi compressors are prized for their durability, modern units offer quieter operation, better fuel efficiency, and integrated diagnostics. However, for those committed to restoration or operating in off-grid environments, retrofitting legacy units can be rewarding.
Retrofit ideas:

• Replace mechanical unloaders with electronic solenoid valves
  
• Add an automatic drain valve to reduce manual maintenance
  
• Upgrade fuel systems with EFI kits for smoother startup
  
• Install solar-powered battery chargers for electric start systems
  

A technician in Texas converted a trailer-mounted LeRoi to run on propane and added a remote start system. The unit now powers irrigation pumps in a remote field with minimal oversight.
Conclusion
LeRoi air compressors represent a bygone era of industrial machinery—built to last, easy to service, and mechanically honest. While parts may be scarce and documentation limited, their core design invites restoration and customization. For those willing to invest time and ingenuity, a vintage LeRoi can still deliver reliable compressed air in the most demanding environments. In a world of disposable machines, the LeRoi stands as a testament to mechanical endurance.