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The IHI 80NX and Its Hydraulic System Design
The IHI 80NX is a mid-size compact excavator produced by Ishikawajima-Harima Heavy Industries, a Japanese manufacturer known for its precision engineering and durable components. With an operating weight of approximately 8 metric tons and a digging depth of over 14 feet, the 80NX was designed for urban infrastructure, utility trenching, and light demolition. Its hydraulic system is central to its performance, powering the boom, arm, bucket, and travel motors with precision and responsiveness.
The hydraulic tank on the 80NX is mounted low in the chassis, supported by brackets that absorb vibration and distribute weight. While robust, this design is vulnerable to stress fractures if mounting bolts are left loose or if the machine experiences heavy impact—especially from above.
Terminology Notes
A seepage was observed at the bottom mounting bracket of the hydraulic tank. Upon inspection, the bracket appeared to have been left loose by a previous owner, allowing vibration to propagate stress into the weld seam. Additionally, the tank had suffered a heavy impact from above, likely causing a hairline crack that extended downward.
Key symptoms included:
The repair process involved several stages:
Operator Anecdotes and Practical Advice
One operator in Georgia shared that the tank had likely been hit by a falling object during transport or site work. The impact caused a stress fracture that worsened over time due to vibration. After removing the tank and inspecting it, he opted for a full rebuild rather than replacement.
A technician recommended pickling the tank before welding to ensure clean adhesion and prevent porosity. He also emphasized the importance of pressure testing after repair, noting that even small cracks can reopen under hydraulic pressure.
Another mechanic suggested reinforcing the bracket area with gussets or thicker weld beads to prevent future failures, especially if the machine operates on rocky terrain.
Preventive Measures and Long-Term Solutions
A seeping hydraulic tank on the IHI 80NX can be repaired effectively with careful inspection, welding, and pressure testing. While replacement is costly and time-consuming, a well-executed rebuild restores function and extends service life. In compact excavators, where hydraulic integrity is paramount, even a small crack deserves serious attention. With the right tools and strategy, operators can turn a costly leak into a durable fix—and keep the machine digging for years to come.
The IHI 80NX is a mid-size compact excavator produced by Ishikawajima-Harima Heavy Industries, a Japanese manufacturer known for its precision engineering and durable components. With an operating weight of approximately 8 metric tons and a digging depth of over 14 feet, the 80NX was designed for urban infrastructure, utility trenching, and light demolition. Its hydraulic system is central to its performance, powering the boom, arm, bucket, and travel motors with precision and responsiveness.
The hydraulic tank on the 80NX is mounted low in the chassis, supported by brackets that absorb vibration and distribute weight. While robust, this design is vulnerable to stress fractures if mounting bolts are left loose or if the machine experiences heavy impact—especially from above.
Terminology Notes
- Hydraulic Tank: A reservoir that stores hydraulic fluid, typically made of steel and pressurized during operation.
- Mounting Bracket: A welded or bolted support structure that secures the tank to the frame.
- Pickling: A chemical cleaning process that removes rust and contaminants from metal surfaces before welding.
- Pressure Testing: A diagnostic method that involves sealing and pressurizing a tank to detect leaks or cracks.
A seepage was observed at the bottom mounting bracket of the hydraulic tank. Upon inspection, the bracket appeared to have been left loose by a previous owner, allowing vibration to propagate stress into the weld seam. Additionally, the tank had suffered a heavy impact from above, likely causing a hairline crack that extended downward.
Key symptoms included:
- Visible hydraulic fluid seepage near the bracket weld
- Discoloration and paint bubbling around the affected area
- No major leaks, but consistent fluid loss over time
- Evidence of prior impact on the tank’s top surface
The repair process involved several stages:
- Drain the hydraulic fluid and remove the tank from the machine
- Strip paint from the affected area to expose the crack
- Seal and pressurize the tank to confirm leak location
- Cut away the top plate and bottom bracket to access damaged metal
- Pickle the surface to prepare for welding
- Weld the crack and reinforce the bracket area
- Pressure test the tank post-repair to ensure integrity
- Repaint and reinstall the tank
Operator Anecdotes and Practical Advice
One operator in Georgia shared that the tank had likely been hit by a falling object during transport or site work. The impact caused a stress fracture that worsened over time due to vibration. After removing the tank and inspecting it, he opted for a full rebuild rather than replacement.
A technician recommended pickling the tank before welding to ensure clean adhesion and prevent porosity. He also emphasized the importance of pressure testing after repair, noting that even small cracks can reopen under hydraulic pressure.
Another mechanic suggested reinforcing the bracket area with gussets or thicker weld beads to prevent future failures, especially if the machine operates on rocky terrain.
Preventive Measures and Long-Term Solutions
- Inspect mounting brackets regularly for looseness or stress marks
- Torque bracket bolts to spec during routine service
- Install protective guards above the tank to prevent impact damage
- Use high-quality hydraulic fluid to reduce corrosion risk
- Document tank repairs and pressure test results for future reference
A seeping hydraulic tank on the IHI 80NX can be repaired effectively with careful inspection, welding, and pressure testing. While replacement is costly and time-consuming, a well-executed rebuild restores function and extends service life. In compact excavators, where hydraulic integrity is paramount, even a small crack deserves serious attention. With the right tools and strategy, operators can turn a costly leak into a durable fix—and keep the machine digging for years to come.
