Searching for a 1995 BD2G Dozer Engine

[MikePhua]

The Komatsu BD2G Legacy
The BD2G crawler dozer was part of Komatsu’s compact dozer lineup in the 1990s, designed for light construction, grading, and land clearing. Komatsu, founded in 1921 in Japan, had by then become the world’s second-largest construction equipment manufacturer. The BD2G was a continuation of the BD series, which had gained popularity for its hydrostatic transmission, compact footprint, and ease of operation. It was particularly favored in Southeast Asia, Australia, and parts of North America for small-scale earthmoving tasks.
The BD2G was powered by a Komatsu 4D95S-W diesel engine, a naturally aspirated four-cylinder unit producing around 60 horsepower. The dozer featured a hydrostatic drive system, allowing smooth, clutch-free operation and precise control. Its operating weight hovered around 8,000 to 9,000 pounds, making it ideal for tight job sites and agricultural use.
Engine Characteristics and Common Failures
The 4D95S-W engine is part of Komatsu’s 95-series, known for its mechanical simplicity and reliability. It uses direct injection and a gear-driven camshaft, with a compression ratio of approximately 18:1. The engine block is cast iron, and the cylinder head is aluminum alloy. Cooling is achieved via a belt-driven water pump and radiator system.
Terminology Note: “Direct injection” means fuel is sprayed directly into the combustion chamber, improving efficiency and cold-start performance. “Compression ratio” refers to the volume difference between the cylinder’s maximum and minimum capacity, affecting power and fuel economy.
Common engine issues include:

• Cracked cylinder heads due to overheating
  
• Worn piston rings causing blow-by
  
• Injector failure leading to poor combustion
  
• Timing gear wear affecting valve timing
  

A contractor in Queensland shared how his BD2G lost power during a grading job. After inspection, he found a cracked head and a warped block caused by prolonged overheating. He sourced a replacement engine from a retired PC50 excavator, which shared the same 4D95 platform, and adapted it with minor modifications.
Hydrostatic Transmission and Engine Compatibility
The BD2G’s hydrostatic transmission is tightly integrated with the engine. It uses a variable displacement pump and motor system, allowing infinite speed control and directional changes without gear shifting. This system requires a compatible engine with a matching bell housing and torque characteristics.
When replacing the engine, it’s critical to:

• Match the flywheel diameter and bolt pattern
  
• Ensure the crankshaft output matches the pump coupling
  
• Verify engine mounts and oil pan clearance
  
• Maintain hydraulic pressure specifications (typically 3,000 PSI)
  

Some operators have successfully retrofitted Kubota V3300 engines, but this requires custom adapters and recalibration of the hydraulic system.
Parts Availability and Salvage Strategies
Finding a replacement 4D95S-W engine can be challenging due to limited production and regional distribution. Strategies include:

• Contacting Komatsu dealers for remanufactured units
  
• Searching salvage yards for compatible engines from PC50, D20, or FG series machines
  
• Exploring marine engine variants with similar blocks
  
• Rebuilding the existing engine using aftermarket kits
  

A forestry operator in Oregon rebuilt his BD2G engine using a kit sourced from a supplier in Malaysia. The kit included pistons, rings, gaskets, and bearings, and cost under $1,200. He documented the rebuild process and noted that the cylinder liner installation required a custom press due to tight tolerances.
Cooling System and Preventive Maintenance
Overheating is a leading cause of engine failure in BD2G dozers. Preventive steps include:

• Flushing coolant every 1,000 hours
  
• Replacing the thermostat annually
  
• Cleaning radiator fins monthly
  
• Checking belt tension and replacing worn belts
  

A municipal crew in the Philippines reported frequent overheating during road grading. They discovered that the radiator had been clogged with volcanic ash, reducing airflow. After installing a mesh guard and switching to high-flow coolant, the issue was resolved.
Fuel System and Cold Start Tips
The BD2G uses a mechanical fuel injection pump and glow plugs for cold starting. In colder climates, starting difficulties are common. Recommendations include:

• Using winter-grade diesel
  
• Installing a block heater
  
• Replacing glow plugs every 500 hours
  
• Bleeding the fuel system after filter changes
  

A farmer in Hokkaido noted that switching to synthetic engine oil improved cranking speed during winter, reducing starter strain and fuel consumption.
Engine Swap Considerations
When sourcing a replacement engine, consider:

• Compatibility with hydrostatic drive
  
• Availability of parts and service manuals
  
• Emissions compliance if operating in regulated zones
  
• Long-term reliability and support
  

Some operators opt for complete powertrain swaps, replacing both engine and transmission with modern equivalents. This can cost upwards of $10,000 but may extend the machine’s life by 15–20 years.
Operator Stories and Field Adaptations
In 2011, a small contractor in New Mexico faced a dilemma when his BD2G’s engine seized during a flood cleanup. With no replacement available locally, he adapted a Mitsubishi S4L2 engine from a generator, fabricating custom mounts and modifying the intake manifold. Though not ideal, the dozer returned to service within two weeks.
Another operator in Thailand converted his BD2G to run on biodiesel, replacing fuel lines and seals with compatible materials. He reported smoother operation and reduced fuel costs, though cold starts became more difficult.
Conclusion
The 1995 Komatsu BD2G dozer remains a valuable tool for compact earthmoving tasks. Its hydrostatic transmission and rugged design make it ideal for precision grading and land clearing. However, engine failure—especially involving the 4D95S-W—can pose serious challenges. With careful planning, resourceful sourcing, and mechanical ingenuity, operators can restore or upgrade their machines, keeping them productive for years to come. The BD2G’s legacy lives on in the stories of those who refuse to let a seized motor end a machine’s journey.