Terex S-11E Drive System Troubleshooting

[MikePhua]

Introduction
The Terex S-11E elevating motor scraper, introduced in the early 1970s, was designed for efficient earthmoving tasks. However, like many vintage machines, it can experience drive system issues over time. One common problem reported by operators is overheating of the power unit, torque converter, or hydraulic clutch, leading to operational failures. This article delves into potential causes and solutions for these drive system issues.
Understanding the Drive System
The S-11E's drive system comprises several key components:

• Power Unit: Converts engine power to hydraulic energy.
  
• Torque Converter: Transfers and amplifies engine torque to the drive train.
  
• Hydraulic Clutch: Engages and disengages the drive to the wheels.
  
• Final Drive Motors: Transmit power to the wheels, enabling movement.
  

Common Issues and Causes

1. Overheating Components
   Operators have reported that after several loads, the power unit and associated components overheat to approximately 250°F, causing the scraper to cease movement. This is often accompanied by the driveshaft stopping. Such overheating can result from:
   • Insufficient Hydraulic Fluid: Low fluid levels can cause inadequate lubrication and cooling.
     
   • Clogged Oil Cooler: Debris or sludge buildup can impede heat dissipation.
     
   • Worn Hydraulic Components: Aging parts may not function efficiently, leading to increased friction and heat.
     
2. Sluggish or Unresponsive Movement
   When cold, the scraper may only move in lower gears (1 or 2). This sluggishness can be attributed to:
   • Thickened Hydraulic Fluid: Cold temperatures can cause fluid to thicken, affecting flow and responsiveness.
     
   • Faulty Torque Converter: A malfunctioning converter may not transmit power effectively.
     
   • Hydraulic Clutch Issues: Problems with the clutch can prevent proper engagement, leading to movement issues.
     

Diagnostic and Maintenance Steps
To address these issues, consider the following steps:

• Check Hydraulic Fluid Levels: Ensure fluid is at the recommended levels and is of the correct type.
  
• Inspect Oil Cooler: Clean or replace the oil cooler if it's clogged or inefficient.
  
• Examine Hydraulic Components: Look for signs of wear or damage in the power unit, torque converter, and hydraulic clutch.
  
• Test Hydraulic Pressure: Verify that system pressures are within manufacturer specifications.
  
• Replace Worn Parts: If components are found to be faulty, replace them with OEM parts to ensure compatibility and performance.
  

Conclusion
The Terex S-11E, while a robust machine, can experience drive system issues due to age and wear. Regular maintenance and timely repairs are crucial to keep the scraper operating efficiently. By understanding the common problems and their causes, operators can take proactive measures to ensure the longevity and reliability of their equipment.