Locating the Oil Temperature Sensor on a Case 580SK Phase 3 Backhoe

[MikePhua]

The oil temperature sensor on the Case 580SK Phase 3 backhoe is mounted on one of the hydraulic return lines just before the hydraulic pump—not on the transaxle or the hydraulic oil return housing as commonly assumed.
Case 580SK background and hydraulic system evolution
The Case 580SK was introduced in the early 1990s as part of the long-running 580 series of tractor-loader-backhoes. The “SK” designation marked a significant update over the earlier “K” model, with improvements in hydraulic performance, operator comfort, and emissions compliance. The Phase 3 variant, often found in export markets like South Africa and Europe, incorporated regional design changes, including different sensor placements and hydraulic routing.
The 580SK features:

• A 4-cylinder diesel engine (typically Case 4-390 or Cummins B3.9)
  
• Open-center hydraulic system with gear pump
  
• Mechanical shuttle transmission
  
• Dual hydraulic return lines routed to the reservoir
  
• Instrument cluster with analog gauges and warning lights
  

The oil temperature sensor plays a critical role in monitoring hydraulic fluid temperature and triggering warnings or shutdowns if overheating occurs.
Common misconceptions about sensor location
Many technicians expect the oil temperature sensor to be located:

• On the transaxle housing
  
• Near the hydraulic oil filter base
  
• On the return manifold at the hydraulic tank
  

However, on certain Phase 3 units—especially those assembled in France or configured for export—the sensor is relocated to a hydraulic return line upstream of the pump. This design allows for more accurate temperature readings under load, as the fluid has not yet passed through the cooler or reservoir.
Identifying the sensor on the machine
To locate the sensor:

• Trace the hydraulic return lines from the loader and backhoe valves toward the pump
  
• Look for a threaded sensor body with a single wire or two-pin connector
  
• The sensor is typically mounted in a welded boss or threaded T-fitting
  
• It may be partially obscured by hoses or brackets near the right side of the engine compartment
  

Once located, the sensor can be tested with a multimeter. Resistance should decrease as temperature increases. A faulty sensor may cause erratic gauge readings or failure to trigger overheat warnings.
Service tips and replacement advice

• Always depressurize the hydraulic system before removing the sensor
  
• Use thread sealant compatible with hydraulic oil
  
• Torque to manufacturer spec to avoid cracking the fitting
  
• If replacing the sensor, match the resistance curve to the original part
  
• Clean surrounding area to prevent contamination during removal
  

One technician in KwaZulu-Natal noted that his imported 580SK had the sensor mounted in a completely different location than the North American service manual indicated. After days of searching, he found it tucked behind a steel bracket near the pump inlet.
Conclusion
The oil temperature sensor on the Case 580SK Phase 3 may not be where most diagrams suggest. On certain international variants, it is installed on a hydraulic return line just before the pump. Understanding this variation is essential for accurate diagnostics and sensor replacement. Always verify sensor location visually and consult region-specific service documentation when available.