Persistent Overheating in the Gehl 4625 Skid Steer with Kubota V2203 Engine

[MikePhua]

The Gehl 4625 and Its Cooling Challenges
The Gehl 4625 is a compact skid steer loader designed for light construction, landscaping, and agricultural work. Manufactured by Gehl Company in the late 1990s and early 2000s, the 4625 was equipped with the Kubota V2203 diesel engine—a naturally aspirated 2.2-liter inline-four known for its reliability and fuel efficiency. Kubota, a Japanese manufacturer with a strong reputation in compact diesel engines, supplied powerplants for numerous skid steers, tractors, and generators during this period.
Despite its reputation for durability, the V2203 engine in the 4625 can suffer from persistent overheating under certain conditions, especially when the cooling system is compromised or improperly configured. Operators have reported temperature spikes reaching 250–260°F even in moderate ambient conditions, which can lead to head warping, gasket failure, and reduced engine life.
Terminology Annotation
- Thermostat: A temperature-sensitive valve that regulates coolant flow between the engine and radiator to maintain optimal operating temperature.
- Flow Restrictor: A device or calibrated passage that limits coolant velocity to ensure proper heat absorption and dissipation.
- Boiling in the Head: A condition where coolant vaporizes inside the cylinder head due to localized overheating, often caused by poor circulation.
- Idle Recovery: The phenomenon where engine temperature drops when running at low RPM due to reduced heat generation and improved cooling efficiency.
Common Causes of Overheating After Cooling System Overhaul
Operators who have replaced major cooling components—including the radiator, water pump, hoses, and even the cylinder head—may still experience overheating. This points to systemic or configuration-related issues rather than isolated part failure.
Key factors include:

• Missing or incorrect thermostat installation
  
• Absence of flow restrictors, allowing coolant to move too quickly through the system
  
• Air pockets trapped in the cylinder head or radiator
  
• Radiator core partially blocked despite external cleaning
  
• Fan belt slippage or incorrect tension reducing airflow
  
• Radiator cap pressure rating too low, allowing premature boiling
  

In one documented case, the machine ran hot after a full cooling system rebuild. The temperature climbed steadily during operation but dropped when idling, suggesting that coolant was circulating too rapidly to absorb heat effectively. This is a classic symptom of a missing thermostat or unrestricted flow path.
A Story from the Appalachian Foothills
In Pennsylvania, a contractor using a Gehl 4625 for barn cleanup noticed the machine overheating after just 90 minutes of work, despite ambient temperatures around 70°F. He had replaced the radiator, water pump, and even installed a new head. Still, the temperature gauge crept past 250°F. After consulting a technician, he discovered that the thermostat had been omitted during reassembly. Installing a proper 180°F thermostat with a bypass hole resolved the issue. The coolant now lingered longer in the head, absorbing heat before returning to the radiator. The machine ran cooler and more consistently, even under load.
Recommendations for Diagnosing and Resolving Overheating
To address persistent overheating:

• Confirm thermostat presence and verify temperature rating (typically 180°F for V2203)
  
• Ensure thermostat includes a bypass or jiggle valve to allow air bleeding
  
• Inspect radiator core for internal blockage using infrared temperature scanning
  
• Check fan belt tension and pulley alignment
  
• Use a radiator cap rated for 13–16 psi to raise boiling point
  
• Bleed the cooling system thoroughly after service to remove trapped air
  
• Consider installing a coolant flow restrictor if thermostat is removed for testing
  

If overheating persists, test coolant flow rate and temperature differential between inlet and outlet hoses. A minimal temperature drop across the radiator suggests poor heat exchange.
Preventative Maintenance and Long-Term Solutions
To prevent future overheating:

• Flush cooling system annually with distilled water and approved coolant
  
• Replace thermostat every 1,000 hours or during major service
  
• Clean radiator fins regularly and inspect for bent or clogged passages
  
• Monitor coolant level and color; milky or rusty fluid indicates contamination
  
• Install a temperature gauge with audible alarm for early warning
  
• Use OEM or high-quality aftermarket parts to ensure proper fit and function
  

For machines operating in dusty or high-debris environments, consider adding a debris screen or reversing fan to improve airflow and reduce clogging.
Conclusion
Overheating in the Gehl 4625 skid steer equipped with a Kubota V2203 engine is often caused by coolant flow mismanagement, not component failure. Missing thermostats, unrestricted circulation, and poor air bleeding can lead to localized boiling and high operating temperatures. With careful inspection and proper configuration, the cooling system can be restored to reliable performance. For operators relying on these compact workhorses, understanding the nuances of coolant dynamics is essential to keeping the machine productive and protected.