Komatsu D65E Steering Problem

[MikePhua]

Overview of the Issue
Owners of the Komatsu D65E‑series (especially the D65E‑6) often report that the steering system loses prime, requires frequent bleeding, or fails to steer properly. Symptoms include recirculating oil, foaming fluid, and the tracks not responding as expected even when the levers and brake pedals are used correctly.
Common Causes

1. Air Ingestion / Loss of Prime
   • The steering pump may suck in air if there is a leak on the suction side.
     
   • Worn or hardened suction lines (rubber hoses) can introduce air, reducing system efficiency.
     
   • Loose or clogged suction strainers under the floor can compromise oil draw, causing pump cavitation.
     
2. Worn Steering Pump
   • Several technicians on forums conclude the steering pump is worn when repeated bleeding doesn’t fix loss of prime.
     
   • Replacing the pump has resolved the issue for some users, restoring consistent steering fluid pressure.
     
3. Hydraulic Clutch or Band Wear
   • The steering system in these dozers uses clutch packs and brake bands. Wear in these components can allow fluid to escape internally, reducing pressure needed for steering.
     
   • Duplicate leaks or internal losses may make the system feel “airy” or weak, even if there is no large visible external leak.
     
4. Low or Contaminated Steering Oil
   • Incorrect oil level or degraded hydraulic fluid can lead to foaming, worsening performance and creating “air” symptoms.
     
   • Because steering and transmission have separate oil sumps, contamination or overfill can lead to cross issues, but that’s less common.
     

Diagnostic Steps

• Remove the floor plates on the operator’s left side to access the steering filter housing and suction strainer.
  
• Press a hydraulic pressure gauge into the steering valve test port (often located at the back of the machine) and run the engine. Pressure should reach around 250–300 psi during operation.
  
• Inspect suction hoses for cracking, pinholes, or anything that might let air in.
  
• Check steering fluid level at the correct fill port. On many D65E models, the fill/check plug is on the rear, above the final drive.
  
• If the steering pump is suspect, remove and inspect it or replace it, especially if air ingestion or foaming persists.
  

Solutions

• Fix or Replace Suction Lines: Use quality hoses, checked for rigidness and free of cracks, and ensure all fittings are tight.
  
• Bleed Properly: After any service, purge air from the system via the bleed plug on the steering filter housing.
  
• Replace Steering Pump: A known remedy. Users report good results after installing a new or remanufactured pump.
  
• Maintain Fluid: Use recommended hydraulic oil, keep it clean, and replace if contaminated, foamy, or discolored.
  
• Monitor Clutches/Bands: During service, check the condition of steering clutches and brake bands. Excessive wear might require rebuild or replacement.
  

Real‑World Example
One D65E‑6 owner noted that after bleeding and topping off, the machine would steer for a while but then lose prime and foam – especially in warm weather.  Another owner discovered that worn steering clutches (pads) were the culprit and planned to address that after stabilizing the fluid system.
Conclusion
Steering issues on the Komatsu D65E class often boil down to air entering the system or a worn steering pump. By carefully inspecting the suction path, ensuring correct fluid level, bleeding properly, and replacing worn components, most users can restore reliable steering performance. Regular maintenance and vigilance are key to preventing recurring problems.