Troubleshooting the Drive System of a Case 850K Series 2 Dozer

[MikePhua]

The Case 850K Series 2 is a powerful dozer designed for heavy-duty construction work. However, like all heavy machinery, it can experience mechanical issues that need prompt attention. One such issue that operators often face is the failure of the drive system to engage. This article provides a comprehensive guide on understanding, diagnosing, and fixing issues related to the drive system of a Case 850K Series 2 dozer. We'll explore the possible causes of this problem, steps for troubleshooting, and key considerations for repair.
Understanding the Drive System of the Case 850K Series 2
The drive system of a dozer like the Case 850K Series 2 is essential for its operation. It powers the tracks, allowing the machine to move forward, backward, and turn. The system consists of several components, including the transmission, the torque converter, the hydraulic pumps, and the differential drive. When any of these components fail or malfunction, the entire system can be affected.
The 850K Series 2, like other modern dozers, utilizes a hydrostatic drive system. This means that the machine's power is transmitted via hydraulic fluids rather than mechanical gears. While hydrostatic systems are known for their efficiency and ease of use, they also require regular maintenance and careful attention to avoid operational issues.
Common Causes for the Drive System Not Engaging
When the drive system of the Case 850K Series 2 fails to engage, it can be due to several reasons. Some of the most common causes include:

1. Hydraulic Fluid Issues:
   • Low Hydraulic Fluid: Insufficient hydraulic fluid levels can result in a loss of pressure, preventing the drive system from engaging properly. This could be caused by leaks, improper fluid levels, or contamination of the fluid.
     
   • Contaminated Hydraulic Fluid: If the hydraulic fluid is contaminated with dirt, water, or other foreign particles, it can impair the operation of the hydraulic pumps and valves. This can lead to a loss of pressure or erratic behavior in the drive system.
     
2. Faulty Hydraulic Pumps or Valves:
   • The hydraulic pumps or control valves that direct fluid to the drive motors may be malfunctioning. If these components fail or become clogged, the flow of fluid to the drive system will be disrupted, causing the dozer to fail to move.
     
3. Electrical System Problems:
   • Modern dozers like the Case 850K Series 2 rely heavily on the electrical system to control various functions, including the engagement of the drive system. Faulty wiring, blown fuses, or issues with the electrical control modules could result in the drive system not engaging.
     
4. Transmission or Torque Converter Failure:
   • The transmission and torque converter play a significant role in the drive system’s performance. If either of these components fails, it can prevent the dozer from moving. Signs of transmission or torque converter failure include slipping, overheating, or a complete lack of power to the tracks.
     
5. Drive Motor Issues:
   • The drive motors themselves may also be the source of the problem. If the drive motors are not receiving the required pressure or if they are damaged, the tracks will fail to move.
     
6. Control Linkage or Mechanical Failures:
   • Issues with the control linkage, such as the shift linkage or control cables, can prevent the operator from engaging the drive system. Similarly, broken or worn-out mechanical parts can hinder the machine's operation.
     

Steps for Diagnosing and Fixing the Problem
To effectively diagnose and fix the issue with the drive system of the Case 850K Series 2, follow these steps:

1. Check Hydraulic Fluid Levels:
   • Start by inspecting the hydraulic fluid levels. If they are low, top up the fluid and check for leaks. Make sure you’re using the correct type of hydraulic fluid as specified in the operator’s manual.
     
   • If the fluid looks dirty or contaminated, perform a fluid change and replace the filters. Clean hydraulic fluid is crucial for proper system operation.
     
2. Inspect the Hydraulic System:
   • Check the hydraulic lines for leaks, cracks, or blockages. If any leaks are found, repair or replace the affected hoses.
     
   • Test the hydraulic pressure to ensure it is within the correct range. If the pressure is low, it could indicate a problem with the hydraulic pump, valves, or the fluid itself.
     
3. Test the Electrical System:
   • Check the fuses and wiring that control the drive system. Look for any signs of damage, corrosion, or loose connections. Ensure that the control modules are functioning correctly.
     
   • Test the electrical components such as sensors and solenoids. Faulty sensors or solenoids can prevent the system from engaging.
     
4. Inspect the Transmission and Torque Converter:
   • Check the transmission fluid level and condition. If the fluid is low or burnt, replace it with fresh fluid as specified by the manufacturer.
     
   • Inspect the torque converter for signs of wear or damage. If the torque converter is malfunctioning, it may need to be rebuilt or replaced.
     
5. Examine the Drive Motors:
   • Test the drive motors to ensure they are receiving proper hydraulic pressure. If the motors are not functioning, you may need to rebuild or replace them.
     
   • Check for any signs of excessive wear or damage in the motors. If the motors are faulty, they will need to be serviced or replaced.
     
6. Inspect Control Linkages:
   • Check the shift linkage, cables, and control handles for any signs of wear or damage. If the linkage is faulty, it may need to be adjusted or replaced to restore proper operation.
     

Preventive Maintenance for the Case 850K Series 2
To avoid similar issues with the drive system in the future, it’s essential to implement a routine maintenance schedule. Regular checks and upkeep can prevent many of the common problems associated with hydraulic systems and drive components.

1. Regular Fluid Checks: Make it a habit to check hydraulic fluid levels regularly and change the fluid as per the manufacturer’s recommendations. Keeping the fluid clean will help maintain optimal performance.
   
2. Monitor Hydraulic Pressure: Periodically test the hydraulic pressure to ensure it is within the correct range. Low pressure could indicate a problem with the pump or other components.
   
3. Electrical System Inspections: Inspect the wiring and electrical components frequently to prevent issues related to electrical control. Make sure all connectors are clean and free from corrosion.
   
4. Track Wear and Tear: Regularly check for wear on the tracks and undercarriage components. Worn-out parts can put unnecessary strain on the drive system and lead to premature failure.
   
5. Consult the Operator’s Manual: Always refer to the operator’s manual for specific maintenance instructions, fluid specifications, and troubleshooting steps. Following the manual’s guidelines will ensure the longevity of your Case 850K Series 2.
   

Conclusion
Dealing with a drive system that won’t engage on your Case 850K Series 2 dozer can be frustrating, but with proper diagnosis and maintenance, most issues can be resolved. By following the steps outlined above, you can troubleshoot the problem effectively and restore your machine to full functionality. Remember that regular maintenance is key to preventing future issues, and addressing minor problems early on can save you time and money in the long run.
With the right knowledge and attention to detail, your Case 850K Series 2 can continue to perform reliably on the job site for years to come.