Hydraulic Oil Change for Hitachi ZX35U-3: A Comprehensive Guide

[MikePhua]

Maintaining the hydraulic system of construction equipment is crucial for its longevity and optimal performance. One of the most important aspects of hydraulic system maintenance is changing the hydraulic oil. The Hitachi ZX35U-3, a compact mini excavator, is a reliable machine used in various industries, but like all machinery, it requires periodic maintenance to ensure its smooth operation. This article offers a detailed guide on changing the hydraulic oil for the Hitachi ZX35U-3, including the necessary steps, tips, and considerations for keeping the hydraulic system in top condition.
Why Change Hydraulic Oil?
Hydraulic oil plays a critical role in the operation of construction machinery like the Hitachi ZX35U-3. It provides the necessary power for hydraulic components such as pumps, cylinders, and motors. Over time, hydraulic oil can degrade due to contamination, high heat, and prolonged use, which can cause reduced efficiency, increased wear on components, and even complete system failure if left unaddressed.
Changing the hydraulic oil on time helps to:

• Ensure Consistent Hydraulic Performance: Fresh oil ensures optimal power delivery to hydraulic components.
  
• Extend Component Life: Clean oil reduces wear and tear on expensive hydraulic pumps, valves, and motors.
  
• Prevent Contamination: Old oil can become contaminated with dirt, metal shavings, and water, which could damage the system.
  
• Maintain Fluid Viscosity: Over time, oil viscosity changes, affecting its ability to lubricate the system. Replacing the oil ensures that the correct viscosity is maintained.
  

Tools and Supplies Needed
Before starting the hydraulic oil change, gather the following tools and supplies:

• Hydraulic Oil (Correct Type and Amount): Ensure you use the hydraulic oil recommended by Hitachi for the ZX35U-3. Typically, this information can be found in the owner’s manual. Ensure the oil is compatible with the operating environment (temperature, pressure).
  
• Drain Pan: To catch the used oil.
  
• Wrench Set: For loosening bolts on the drain plugs and filters.
  
• New Hydraulic Filter: It is essential to replace the hydraulic filter when changing the oil to avoid contamination.
  
• Gloves and Safety Gear: Always wear safety gear when handling hydraulic oil.
  
• Clean Rags: For wiping any excess oil and cleaning up the area.
  
• Funnel: To add fresh hydraulic oil easily.
  
• Jack and Stand: In case you need to lift the excavator for better access to the hydraulic system.
  
• Oil Disposal Container: To dispose of the old oil in an environmentally friendly manner.
  

Steps for Changing Hydraulic Oil on Hitachi ZX35U-3
1. Prepare the Excavator

• Turn Off the Engine: Always make sure the engine is turned off and the equipment is on level ground before starting any maintenance procedure.
  
• Lift the Excavator: If necessary, use a jack to slightly lift the excavator to provide more access to the hydraulic system’s drain plugs. Ensure the machine is secure before proceeding.
  
• Remove the Key: For safety, remove the key from the ignition to prevent accidental startup while working.
  

2. Locate the Hydraulic Oil Drain Plug

• The hydraulic system of the ZX35U-3 has a drain plug that is used to empty the old hydraulic oil. Locate the drain plug by referencing the owner’s manual for the exact location. In most cases, the drain plug will be located near the hydraulic reservoir or pump.
  
• Place your drain pan under the drain plug to catch the used oil as it drains out.
  

3. Drain the Hydraulic Oil

• Remove the Drain Plug: Use a wrench to carefully remove the drain plug and allow the old hydraulic oil to drain completely into the pan. Be cautious as the oil may be hot if the machine was recently used.
  
• Let the Oil Drain: Allow the oil to drain for at least 15 to 30 minutes. This ensures that most of the oil is removed from the system, including any contaminants.
  

4. Replace the Hydraulic Filter

• After draining the old oil, locate the hydraulic filter, which is typically mounted on the hydraulic pump or reservoir.
  
• Use a wrench or filter wrench to remove the old filter. Be sure to dispose of it properly.
  
• Lubricate the New Filter: Before installing the new filter, apply a small amount of fresh hydraulic oil to the rubber gasket on the new filter. This helps ensure a proper seal and prevents leaks.
  
• Install the new filter by hand-tightening it into place. Ensure that it is securely in position.
  

5. Refill the Hydraulic System with New Oil

• Install the Drain Plug: Once the oil has drained and the filter has been replaced, reattach the drain plug securely to prevent any oil from leaking.
  
• Refill the Hydraulic Reservoir: Using a funnel, carefully pour the new hydraulic oil into the reservoir. Be sure to follow the manufacturer’s recommended oil type and amount.
  
• Check the Oil Level: After filling the reservoir, check the oil level using the dipstick (if available). Add more oil if necessary to reach the proper level.
  

6. Start the Excavator and Check for Leaks

• Start the Engine: Start the excavator and let the engine run for a few minutes to allow the new oil to circulate through the hydraulic system.
  
• Check for Leaks: While the engine is running, check the hydraulic filter, drain plug, and other areas for leaks. Tighten any loose components to prevent further oil loss.
  
• Operate the Hydraulic System: Move the joystick and operate the hydraulic controls to make sure that the system is functioning smoothly and the oil is circulating properly.
  

7. Dispose of the Old Oil

• Dispose of the used hydraulic oil in an environmentally responsible manner. Many auto shops, recycling centers, and service stations accept used oil for proper disposal. Never dispose of hydraulic oil in regular trash or pour it down drains.
  

Common Issues to Look Out For
While performing a hydraulic oil change on the Hitachi ZX35U-3, there are a few issues to keep in mind:
1. Incorrect Oil Type or Viscosity
Using the wrong type of hydraulic oil can lead to poor performance and potential damage to the hydraulic system. Always refer to the owner's manual to select the correct oil type and viscosity for your operating conditions.
2. Contaminated Oil
If the hydraulic oil is contaminated with water, dirt, or metal particles, it can cause excessive wear on the system. This is why it’s important to replace the filter during each oil change and properly dispose of the old oil.
3. Oil Leaks
Leaks around the drain plug, filter, or seals are common problems. Always inspect these areas for tightness and proper seals to prevent future oil loss.
4. Low Oil Level After Refill
If the oil level is low after refilling, it could indicate a hidden leak or that the oil was not fully drained. In such cases, check all seals and joints for leaks and make sure the drain plug was properly replaced.
How Often Should You Change the Hydraulic Oil?
The frequency of hydraulic oil changes depends on several factors, including the machine’s usage, operating conditions, and manufacturer recommendations. Typically, it is advisable to change the hydraulic oil on a mini-excavator like the Hitachi ZX35U-3 every 1,000 to 1,500 operating hours. However, if the machine operates in extreme conditions (such as in dusty or muddy environments), you may need to change the oil more frequently.
Conclusion
Changing the hydraulic oil in your Hitachi ZX35U-3 is a straightforward but vital maintenance task that can extend the life of the hydraulic system and improve the machine’s overall performance. By following the proper steps and using the right tools and oil, you can ensure that your mini-excavator runs efficiently and reliably. Regular maintenance, including hydraulic oil changes, is key to preventing costly repairs and downtime, allowing your equipment to perform optimally for years to come.