Resolving Hydraulic Oil Overheat Alerts in Bobcat T190 Skid Steers

[MikePhua]

The Bobcat T190 and Its Role in Compact Construction
The Bobcat T190 compact track loader was introduced in the early 2000s as part of Bobcat’s push to expand its lineup of mid-sized machines for landscaping, construction, and utility work. Bobcat, founded in 1947 in North Dakota, became a household name in compact equipment by pioneering the skid steer loader. The T190, with its 66-horsepower diesel engine and 1,900-pound rated operating capacity, quickly became a favorite among contractors for its balance of power, maneuverability, and attachment versatility.
By 2010, Bobcat had sold tens of thousands of T190 units globally. Its hydraulic system, designed to power everything from buckets to augers and trenchers, is central to its performance. But like many machines of its era, the T190 is vulnerable to sensor-related issues that can trigger false alerts and disrupt operations.
False Hydraulic Overheat Alerts and Operator Confusion
A recurring issue among T190 owners involves the hydraulic oil temperature alert sounding within seconds of startup. The cooling fan engages aggressively, gauges spike, and then—just as quickly—everything returns to normal. This cycle may repeat multiple times during operation, leading to confusion and concern.
Operators often assume the machine is genuinely overheating, prompting unnecessary shutdowns and inspections. However, in most cases, the hydraulic oil is at normal temperature, and the issue lies in the sensor or its associated circuitry.
Understanding Hydraulic Temperature Sensors and Their Role
Hydraulic temperature sensors monitor fluid temperature and send signals to the machine’s controller. In the T190, the sensor is mounted near the hydraulic filter base and works in tandem with the cooling fan and dashboard alerts.
Key terms:

• Hydraulic temperature sensor: A device that converts fluid temperature into an electrical signal.
  
• Open-loop cooling system: A system where fluid is cooled by air or external radiators without feedback control.
  
• Deadhead condition: When fluid flow is blocked, causing pressure buildup and potential overheating.
  

In the T190, a faulty sensor can send incorrect signals, causing the fan to engage prematurely and triggering false alerts. This not only disrupts workflow but can mask real overheating issues if left unchecked.
Sensor Identification and Replacement Strategy
The T190 uses two sensors near the hydraulic filter base:

• A two-wire sensor for hydraulic temperature
  
• A three-wire sensor for charge pressure
  

Misidentifying these sensors can lead to incorrect replacements. Technicians recommend using wiring diagrams or consulting Bobcat service manuals to confirm the correct unit. Once identified, replacing the hydraulic temperature sensor is straightforward and inexpensive—often under $50.
In one case, a technician in British Columbia replaced a faulty water temperature sensor on a Bobcat A300 during a snowstorm. The symptoms mirrored those of the T190: false alerts, fan activation, and shutdowns. After replacing the sensor, the machine returned to normal operation, highlighting how sensor faults can mimic serious mechanical issues.
Electrical Circuit Vulnerabilities and Diagnostic Tips
If replacing the sensor doesn’t resolve the issue, the fault may lie in the 8V electrical circuit that powers multiple sensors. Potential problems include:

• Damaged wiring harnesses due to vibration or rodent activity
  
• Corroded connectors near the hydraulic filter base
  
• Faulty controller logic or software glitches
  

To diagnose:

• Use a multimeter to check voltage at the sensor terminals
  
• Inspect connectors for moisture, corrosion, or bent pins
  
• Test continuity from the sensor to the controller
  
• Use a scan tool to read live data and confirm sensor output
  

In rare cases, the machine’s controller may be at fault. Replacing or reprogramming the controller should be a last resort after all other diagnostics are exhausted.
Cooling Fan Behavior and Hydraulic System Design
The T190’s cooling fan is hydraulically driven and responds to sensor input. When the sensor falsely reports high temperature, the fan engages at full speed, creating noise and unnecessary wear. Over time, this can lead to premature fan motor failure or increased fuel consumption.
Recommendations to mitigate wear:

• Replace faulty sensors promptly
  
• Monitor fan behavior during startup and operation
  
• Clean cooling fins and radiators to ensure airflow
  
• Use infrared thermometers to verify actual fluid temperature
  

One operator in North Carolina noted that after replacing the sensor, his T190 ran quieter and consumed less fuel—an indirect benefit of restoring proper fan control.
Preventive Maintenance and Long-Term Solutions
To prevent future sensor-related issues:

• Inspect wiring harnesses during routine service
  
• Replace sensors every 2,000–3,000 hours or as needed
  
• Keep hydraulic fluid clean and within recommended temperature ranges
  
• Use OEM or high-quality aftermarket sensors to ensure compatibility
  

Bobcat’s newer models have improved sensor shielding and diagnostic capabilities, but legacy machines like the T190 require manual vigilance.
Conclusion
The hydraulic oil high-temperature alert in the Bobcat T190 is often a symptom of sensor malfunction rather than actual overheating. By understanding the role of the temperature sensor, identifying the correct component, and inspecting the electrical circuit, operators can resolve the issue efficiently. In the world of compact equipment, where uptime is everything, a $50 sensor can be the difference between a productive day and a frustrating shutdown. With proper maintenance and diagnostic awareness, the T190 continues to be a reliable workhorse across job sites worldwide.