Case 1150E Left Track Failure and Drive System Diagnostics

[MikePhua]

The Case 1150E and Its Mechanical Heritage
The Case 1150E crawler dozer was introduced in the late 1980s as part of Case Corporation’s evolution in mid-sized earthmoving equipment. Case, founded in 1842, had already built a reputation for durable agricultural and construction machinery. The 1150E featured a 6-cylinder diesel engine producing approximately 110 horsepower, paired with a hydrostatic transmission and a closed-center hydraulic system. Designed for grading, land clearing, and site prep, the 1150E became a popular choice for contractors and municipalities across North America.
Sales of the 1150E were strong throughout the 1990s, and many units remain in service today due to their mechanical simplicity and robust undercarriage. The hydrostatic drive system, while efficient and responsive, requires precise fluid control and component integrity to function properly—especially when diagnosing issues like a non-responsive track.
Symptoms of Left Track Failure
Operators may encounter a situation where the left track stops pulling entirely, while the right track continues to function. This asymmetrical behavior suggests a localized fault within the drive system rather than a global hydraulic failure. Common symptoms include:

• No movement from the left track in forward or reverse
  
• No unusual noises or grinding during operation
  
• Hydraulic fluid levels within normal range
  
• No visible leaks or broken hoses
  
• Machine starts and idles normally
  

In one case, the machine operated fine for several hours before the left track suddenly stopped responding. The right track continued to push, allowing limited maneuverability, but the machine could not turn or back out of a tight spot.
Hydrostatic Drive System Overview
The Case 1150E uses a dual-path hydrostatic transmission, meaning each track is powered independently by its own hydraulic circuit. This allows for precise steering and variable speed control. Each circuit includes:

• A variable displacement pump
  
• A hydraulic motor
  
• Control valves
  
• Relief valves
  
• Filters and lines
  

The left and right circuits share a common reservoir and cooling system but operate independently. If one track fails, the issue is typically isolated to that circuit’s components.
Potential Causes of Track Failure
When the left track stops pulling, possible causes include:

• Drive motor failure: Internal wear or seal failure can prevent torque transfer.
  
• Pump malfunction: A damaged swash plate or broken shaft can stop fluid flow.
  
• Control valve blockage: Debris or contamination may prevent valve actuation.
  
• Electrical fault: If the machine uses electronic solenoids, a failed wire or connector can disable the valve.
  
• Relief valve stuck open: This can cause fluid to bypass the motor, resulting in no movement.
  
• Coupling or spline failure: Mechanical disconnect between motor and final drive.
  

One technician in Alberta traced a similar issue to a broken spline in the left drive motor. The motor spun internally but failed to transmit torque to the track. Replacement required removing the track frame and sourcing a rebuilt motor.
Diagnostic Procedures and Isolation Techniques
To diagnose the issue, follow a structured approach:

• Visual inspection: Check hoses, connectors, and fluid levels.
  
• Swap control lines: Reverse left and right control lines at the valve block. If the fault moves to the right track, the issue is upstream (pump or valve). If it stays on the left, the motor or final drive is suspect.
  
• Pressure testing: Use gauges to measure output pressure from the pump and input pressure at the motor. Compare left and right readings.
  
• Flow testing: Install a flow meter to verify fluid volume reaching the motor.
  
• Electrical testing: If solenoids are used, check voltage and continuity at connectors.
  
• Mechanical inspection: Remove the motor and inspect splines, couplings, and bearings.
  

Always consult the service manual for pressure specs and test port locations. Use clean tools and avoid introducing contamination during testing.
Repair Strategies and Component Replacement
Once the faulty component is identified, repair options include:

• Replacing the hydraulic motor with a remanufactured unit
  
• Rebuilding the pump if internal damage is found
  
• Cleaning or replacing control valves and relief valves
  
• Repairing or replacing damaged wiring or connectors
  
• Flushing the hydraulic system to remove debris
  

Costs vary depending on the component:

• Hydraulic motor: $1,500 to $3,000
  
• Pump rebuild: $2,000 to $4,000
  
• Valve block: $800 to $1,500
  
• Labor: 10 to 20 hours depending on access and disassembly
  

Some operators choose to upgrade to newer motors with improved seals and bearings. Always verify compatibility with the existing mounting and flow specs.
Preventive Maintenance and System Longevity
To prevent future track failures:

• Change hydraulic fluid every 500 hours or annually
  
• Replace filters every 250 hours
  
• Inspect hoses and fittings monthly
  
• Monitor track response during operation
  
• Use OEM-grade fluid and components
  
• Keep electrical connectors clean and dry
  

One fleet manager in Oregon implemented a quarterly pressure test protocol and reduced hydrostatic failures by 60% over two years. His team logged readings and flagged anomalies before they became breakdowns.
Stories from the Field
A contractor in Georgia shared a story of his 1150E losing left track function during a pond excavation. After swapping control lines and confirming the motor was at fault, he sourced a rebuilt unit from a salvage yard and completed the repair in two days. The machine returned to service and ran another 1,200 hours without issue.
Another operator in Saskatchewan found that a loose connector on the left solenoid valve was intermittently disabling the track. After securing the wire and applying dielectric grease, the problem vanished.
Conclusion
The Case 1150E remains a reliable and capable dozer, but its hydrostatic drive system demands careful attention. When a track stops pulling, methodical diagnostics and component isolation are key to restoring function. With proper maintenance and timely repairs, these machines can continue pushing, grading, and clearing for decades—one track at a time.