10-15-2025, 12:42 PM
Model Overview and Production History
The Komatsu D31P-18 is a mid-size crawler dozer designed for grading, site preparation, and light earthmoving. Part of Komatsu’s D31 series, the “P” suffix indicates a low-ground-pressure configuration with wide tracks, ideal for soft terrain such as sand, clay, or swampy conditions. The “-18” designates a specific sub-generation within the D31 family, produced during the late 1980s. Based on serial number data, units like A41935 correspond to a 1989 production year, placing this machine in the final years of the pre-electronic era before Komatsu transitioned to more advanced hydrostatic and electronically controlled models.
Engine and Powertrain Specifications
This model is powered by the Komatsu 6D95L-1 diesel engine, a naturally aspirated inline-six producing approximately 70 horsepower. The engine features mechanical fuel injection, wet-sleeve cylinder liners, and a gear-driven camshaft. Known for its reliability and ease of service, the 6D95L-1 was widely used across Komatsu’s mid-size dozers and loaders during the 1980s and early 1990s.
The D31P-18 is equipped with a hydrostatic transmission (Hy-Stat), allowing smooth variable-speed control without gear shifting. This system uses dual variable-displacement pumps and motors to drive each track independently, improving maneuverability and reducing operator fatigue. The hydrostatic system also provides dynamic braking and precise blade control, especially useful in finish grading.
Operating Weight and Dimensions
The machine weighs approximately 15,770 pounds (7,150 kg), making it suitable for transport on a standard lowboy trailer without special permits in most jurisdictions. Its wide track pads and long undercarriage provide excellent flotation, with ground pressure typically under 4 psi. Blade options include straight, angle, and six-way configurations, with hydraulic tilt and lift cylinders.
Market Value and Resale Trends
As of 2008, the retail value of a well-maintained D31P-18 was estimated at $19,500 USD, though current values vary based on condition, hours, and regional demand. Machines with under 5,000 hours and documented service history may still fetch $15,000–$18,000 in niche markets. However, parts availability is becoming limited, and some components—especially hydrostatic pumps—may require sourcing from remanufacturers or salvage yards.
Serial Number Decoding and Year Identification
Komatsu serial numbers for the D31P-18 typically begin with an “A” prefix followed by five digits. Production year can be estimated using internal dealer guides or aftermarket reference books. For example:
Maintenance Considerations and Common Issues
Key service points include:
The Komatsu D31P-18 remains a capable and respected crawler dozer in the mid-size class. Its 1989 build year places it in a transitional era of mechanical simplicity and hydraulic refinement. With proper maintenance and attention to hydrostatic components, it can continue performing reliably in grading and site prep roles. For buyers and operators, understanding its specifications and service needs ensures informed ownership and long-term value.
The Komatsu D31P-18 is a mid-size crawler dozer designed for grading, site preparation, and light earthmoving. Part of Komatsu’s D31 series, the “P” suffix indicates a low-ground-pressure configuration with wide tracks, ideal for soft terrain such as sand, clay, or swampy conditions. The “-18” designates a specific sub-generation within the D31 family, produced during the late 1980s. Based on serial number data, units like A41935 correspond to a 1989 production year, placing this machine in the final years of the pre-electronic era before Komatsu transitioned to more advanced hydrostatic and electronically controlled models.
Engine and Powertrain Specifications
This model is powered by the Komatsu 6D95L-1 diesel engine, a naturally aspirated inline-six producing approximately 70 horsepower. The engine features mechanical fuel injection, wet-sleeve cylinder liners, and a gear-driven camshaft. Known for its reliability and ease of service, the 6D95L-1 was widely used across Komatsu’s mid-size dozers and loaders during the 1980s and early 1990s.
The D31P-18 is equipped with a hydrostatic transmission (Hy-Stat), allowing smooth variable-speed control without gear shifting. This system uses dual variable-displacement pumps and motors to drive each track independently, improving maneuverability and reducing operator fatigue. The hydrostatic system also provides dynamic braking and precise blade control, especially useful in finish grading.
Operating Weight and Dimensions
The machine weighs approximately 15,770 pounds (7,150 kg), making it suitable for transport on a standard lowboy trailer without special permits in most jurisdictions. Its wide track pads and long undercarriage provide excellent flotation, with ground pressure typically under 4 psi. Blade options include straight, angle, and six-way configurations, with hydraulic tilt and lift cylinders.
Market Value and Resale Trends
As of 2008, the retail value of a well-maintained D31P-18 was estimated at $19,500 USD, though current values vary based on condition, hours, and regional demand. Machines with under 5,000 hours and documented service history may still fetch $15,000–$18,000 in niche markets. However, parts availability is becoming limited, and some components—especially hydrostatic pumps—may require sourcing from remanufacturers or salvage yards.
Serial Number Decoding and Year Identification
Komatsu serial numbers for the D31P-18 typically begin with an “A” prefix followed by five digits. Production year can be estimated using internal dealer guides or aftermarket reference books. For example:
- Serial A41935 → 1989
- Serial A40000–A42000 → 1988–1989 range
Maintenance Considerations and Common Issues
Key service points include:
- Hydrostatic fluid: Use Komatsu-approved hydraulic oil and change every 1,000 hours
- Final drives: Check for seal leaks and gear oil contamination
- Undercarriage wear: Inspect track chains, rollers, and sprockets every 500 hours
- Cooling system: Flush radiator and replace coolant every 2 years
- Hydrostatic pump cavitation due to contaminated fluid or clogged filters
- Blade lift cylinder leaks from worn seals
- Electrical corrosion in older wiring harnesses, especially near the dash and battery box
The Komatsu D31P-18 remains a capable and respected crawler dozer in the mid-size class. Its 1989 build year places it in a transitional era of mechanical simplicity and hydraulic refinement. With proper maintenance and attention to hydrostatic components, it can continue performing reliably in grading and site prep roles. For buyers and operators, understanding its specifications and service needs ensures informed ownership and long-term value.
