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Summary
Replacing the engine in a Takeuchi TB035 mini excavator requires careful consideration of horsepower, cooling capacity, hydraulic compatibility, and physical fit. Undersized engines often lead to overheating and sluggish hydraulic performance, while sourcing OEM Yanmar units can be costly and difficult.
Takeuchi TB035 Background and Engine Specs
The Takeuchi TB035 was introduced in the late 1990s as part of Takeuchi’s compact excavator lineup. Takeuchi, founded in 1963 in Japan, pioneered the mini excavator category and remains a global leader in compact construction equipment. The TB035 featured a 33-horsepower Yanmar 3TNA84 diesel engine, known for its reliability and compatibility with the machine’s hydraulic system. Thousands of units were sold across North America and Europe, making it a popular choice for contractors and rental fleets.
Terminology and System Overview
Several owners have attempted to replace the original Yanmar engine with Kubota alternatives due to availability and cost. The Kubota V1503 (24 HP) and V1703E (30 HP) are common candidates, but both present challenges:
Successful Replacement with Yanmar 3TN84
A more suitable replacement was found in a Yanmar 3TN84 engine salvaged from a fairway mower. Although naturally aspirated (non-turbo), it matched the original horsepower and fit the engine bay. After installation, the machine ran well but exhibited slow hydraulic functions. This prompted further investigation into pressure and flow characteristics.
Hydraulic Troubleshooting and Recommendations
Sluggish boom, stick, and bucket movements may stem from:
One technician shared that after installing the 3TN84, the machine’s travel motors worked well, but drive power dropped when hot. This was traced to possible bypassing in the swivel seals. Another noted that hydraulic speed is governed by flow, not pressure—highlighting the importance of matching engine output to pump requirements.
Conclusion
Replacing the engine in a Takeuchi TB035 is feasible but requires matching horsepower, RPM, and physical dimensions. Undersized engines may run but will struggle with heat and hydraulic performance. The Yanmar 3TN84 remains the closest match, though sourcing used units from turf equipment or compact tractors may be necessary. Operators should prioritize cooling upgrades, hydraulic diagnostics, and careful engine selection to restore full functionality. With proper planning, the TB035 can continue serving reliably for years to come.
Replacing the engine in a Takeuchi TB035 mini excavator requires careful consideration of horsepower, cooling capacity, hydraulic compatibility, and physical fit. Undersized engines often lead to overheating and sluggish hydraulic performance, while sourcing OEM Yanmar units can be costly and difficult.
Takeuchi TB035 Background and Engine Specs
The Takeuchi TB035 was introduced in the late 1990s as part of Takeuchi’s compact excavator lineup. Takeuchi, founded in 1963 in Japan, pioneered the mini excavator category and remains a global leader in compact construction equipment. The TB035 featured a 33-horsepower Yanmar 3TNA84 diesel engine, known for its reliability and compatibility with the machine’s hydraulic system. Thousands of units were sold across North America and Europe, making it a popular choice for contractors and rental fleets.
Terminology and System Overview
- Horsepower (HP): A measure of engine power output. The TB035 originally used a 33 HP engine.
- Cooling Fan (Electric vs. Manual): Electric fans are compact but may lack airflow; manual fans are belt-driven and typically move more air.
- Hydraulic Flow: Determines the speed of functions like boom, stick, and bucket. Flow is affected by engine RPM and pump capacity.
- Pilot Pressure: Low-pressure hydraulic signal used to control main valves.
- Swivel Seals: Seals in the rotating joint between upper and lower structures; failure can cause hydraulic bypass and weak travel motors.
Several owners have attempted to replace the original Yanmar engine with Kubota alternatives due to availability and cost. The Kubota V1503 (24 HP) and V1703E (30 HP) are common candidates, but both present challenges:
- V1503: Underpowered for the TB035, leading to overheating and sluggish hydraulics.
- V1703E: Closer in power but longer in physical dimensions, requiring frame modifications.
Successful Replacement with Yanmar 3TN84
A more suitable replacement was found in a Yanmar 3TN84 engine salvaged from a fairway mower. Although naturally aspirated (non-turbo), it matched the original horsepower and fit the engine bay. After installation, the machine ran well but exhibited slow hydraulic functions. This prompted further investigation into pressure and flow characteristics.
Hydraulic Troubleshooting and Recommendations
Sluggish boom, stick, and bucket movements may stem from:
- Low engine RPM: Ensure the replacement engine matches the original RPM range.
- Pump mismatch: Confirm the engine’s torque curve supports the hydraulic pump’s demands.
- Relief valve settings: A weak relief valve can limit pressure and flow.
- Swivel joint bypass: Leaking seals can reduce drive motor performance when hot.
- Install hydraulic tees and pressure gauges on slow functions.
- Compare pilot pressure and main pressure under load.
- Swap main pump hoses to isolate valve bank issues.
- Replace electric fan with a larger manual blade to improve cooling.
One technician shared that after installing the 3TN84, the machine’s travel motors worked well, but drive power dropped when hot. This was traced to possible bypassing in the swivel seals. Another noted that hydraulic speed is governed by flow, not pressure—highlighting the importance of matching engine output to pump requirements.
Conclusion
Replacing the engine in a Takeuchi TB035 is feasible but requires matching horsepower, RPM, and physical dimensions. Undersized engines may run but will struggle with heat and hydraulic performance. The Yanmar 3TN84 remains the closest match, though sourcing used units from turf equipment or compact tractors may be necessary. Operators should prioritize cooling upgrades, hydraulic diagnostics, and careful engine selection to restore full functionality. With proper planning, the TB035 can continue serving reliably for years to come.
