John Deere 750J Dozer Troubleshooting Guide

[MikePhua]

The John Deere 750J dozer is a robust and reliable machine, widely used in construction, mining, and land reclamation projects. However, like any heavy equipment, it can experience issues that may affect its performance. This guide provides an in-depth look at common problems faced by 750J dozer operators, along with troubleshooting steps and maintenance tips to ensure optimal performance.
Common Issues and Troubleshooting

1. Hydraulic Pressure Loss
   

A significant issue reported by operators is the sudden loss of hydraulic pressure. This can occur after a hydraulic hose failure, leading to a complete loss of hydraulic function. In one instance, replacing the hydraulic relief valve and pump did not resolve the issue. Further investigation revealed that debris had caused a valve to stick open, located between the batteries and the hydraulic filter. Cleaning the valve restored hydraulic function, highlighting the importance of thorough inspection and cleaning during repairs.

1. Engine Misfire When Warm
   

Some 750J dozers experience engine misfires or rough idling after the engine warms up. This problem can stem from several sources, including:

• Fuel Delivery Issues: A weak fuel lift pump can cause air to enter the fuel system, leading to misfires. Checking the fuel lift pump for consistent pressure is essential.
  
• Injector Problems: Faulty injectors or poor injector timing can disrupt engine performance. Inspecting and testing injectors can help identify such issues.
  
• Sensor Malfunctions: A malfunctioning coolant temperature sensor can cause incorrect fuel mapping, leading to engine problems. Testing the sensor and replacing it if necessary can resolve this issue.
  

Regular maintenance, including draining water or contaminants from the fuel tank and replacing filters, can prevent these problems.

1. Track Misalignment and Steering Issues
   

After replacing hydraulic components like hydro pumps or power shaft couplings, operators have reported track misalignment and unexpected track stoppages. This often indicates the need for track calibration. The calibration process involves:

• Adjusting Steering Control Valves: Ensuring that the steering control valves are properly adjusted can correct steering issues.
  
• Verifying Track Tension: Proper track tension is crucial for smooth operation. Adjusting the track tension as per the manufacturer's specifications can resolve alignment problems.
  
• Checking Hydraulic Fluid Levels: Low or contaminated hydraulic fluid can affect track performance. Ensuring that the hydraulic fluid is at the correct level and in good condition is vital.
  

1. Overheating Issues
   

Overheating can occur rapidly in 750J dozers, often due to thermostat or radiator blockages. Common causes include:

• Sticking Thermostat: A thermostat that doesn't open or closes too early can restrict coolant flow, leading to overheating. Testing the thermostat by removing it and placing it in hot water can determine if it's functioning correctly.
  
• Radiator Blockages: Debris or sediment in the radiator can impede airflow, causing the engine to overheat. Inspecting and cleaning the radiator can prevent this issue.
  
• Faulty Head Gasket: A head gasket failure can allow combustion gases into the cooling system, disrupting coolant flow. Checking for signs of a blown head gasket and replacing it if necessary can resolve this problem.
  

Maintenance Tips
To minimize the risk of these issues, regular maintenance is essential:

• Regularly Inspect and Replace Filters: Fuel, air, and hydraulic filters should be inspected and replaced as per the manufacturer's recommendations to ensure optimal performance.
  
• Monitor Fluid Levels and Quality: Regularly check the levels and condition of engine oil, hydraulic fluid, and coolant. Low or contaminated fluids can lead to various mechanical issues.
  
• Clean Radiator and Cooling System: Periodically clean the radiator and cooling system to prevent overheating and ensure efficient engine operation.
  
• Calibrate Tracks and Steering System: After major repairs or component replacements, calibrate the tracks and steering system to maintain proper alignment and functionality.
  
• Check Electrical Components: Inspect sensors, wiring, and control modules for signs of wear or damage. Faulty electrical components can lead to performance issues.
  

Conclusion
The John Deere 750J dozer is a powerful and versatile machine, but like any complex piece of equipment, it requires regular maintenance and timely troubleshooting to ensure reliable operation. By understanding common issues and implementing proactive maintenance practices, operators can extend the lifespan of their dozers and maintain high productivity levels on the job site.