Most skid steer loaders use a rear-mounted integrated cooling package, which means multiple heat exchangers are arranged together in layers and share a common cooling fan. The entire cooling system is typically installed at the rear of the machine, behind the engine compartment access door.
From the outside to the inside, the cooling package is usually arranged as follows:
Hydraulic oil cooler - positioned on the outermost layer to receive the coolest incoming air first;
Engine radiator - located behind the hydraulic oil cooler to remove engine coolant heat;
Charge air cooler (intercooler) - added on turbocharged models to reduce intake air temperature and improve engine efficiency;
Air conditioning condenser - installed on machines equipped with HVAC systems.
Many modern designs use this layered cooling structure, consisting of a main cooling package (radiator and hydraulic oil cooler), charge air cooler, and A/C condenser.
The cooling package is generally designed to swing out or lift as a complete assembly.
This is not just for convenience or appearance. It provides a dedicated access route for cleaning and maintenance, which is one of the most important design features of the entire cooling system.
It is also worth noting that ultra-compact skid steer loaders may use a side-mounted cooling system because the narrow machine frame does not provide enough space for a full rear cooling package.
Why Are Skid Steer Loaders Especially Sensitive to Heat?
The main reason is that three major heat sources work together, making skid steer loaders different from conventional loaders.
1. Engine Heat Generation
The engine produces heat during diesel combustion, which is removed through the engine coolant system.
This system works similarly to other diesel engines:
The water pump circulates coolant through the engine block;
The thermostat controls coolant flow between small and large circulation loops.
When the engine is cold:
The thermostat remains closed;
Coolant circulates internally through the short loop;
The engine reaches operating temperature faster.
Once the coolant reaches the designed temperature:
The thermostat opens;
Coolant flows through the radiator for full cooling.
2. Hydraulic System Heat - The Main Heat Source
The hydraulic system is usually the biggest contributor to heat buildup.
A skid steer loader controls steering through differential movement of the two sides of the machine:
One side can rotate forward;
The other side can rotate backward;
The machine turns by forcing both sides to move at different speeds or directions.
This steering method creates significant hydraulic load because the system frequently operates under:
Pressure relief conditions;
Flow restriction;
Continuous throttling.
As a result, hydraulic oil temperature can rise rapidly.
Therefore, skid steer loaders are equipped with:
Large-capacity hydraulic oil coolers;
Forced-air cooling systems;
Additional oil cooling capacity on heavy-duty models.
Some larger machines are even equipped with dual hydraulic oil coolers to handle extreme operating conditions.
3. Working Environment Conditions
The operating environment is another major factor.
Skid steer loaders are often used in conditions with:
Dust;
Grass clippings;
Wood chips;
Crop residue;
Construction debris.
These materials can easily enter and accumulate between the cooling fins.
The key point is:
The engine cooling circuit and hydraulic cooling circuit are two completely separate fluid systems, but they share the same airflow.
Hydraulic oil flows through the hydraulic return circuit and enters the oil cooler;
Engine coolant circulates through the water pump and radiator.
The two fluids never mix.
However, if one layer of the cooling core becomes blocked, airflow is restricted. The reduced airflow affects the entire cooling package, causing both systems to lose cooling performance.
This is one of the most common causes of overheating problems in skid steer loaders.
Fan System Highlights: Hydraulic Drive + Variable Speed + Reversible Operation
Traditional construction equipment usually uses an engine-driven fan connected directly by a belt, meaning fan speed changes with engine speed.
Skid steer loaders often use a different approach:
The engine drives a hydraulic pump, which powers a dedicated hydraulic fan motor.
Advantages of Hydraulic Fan Drive
The biggest benefit is that fan speed is independent from engine speed.
The machine controller adjusts fan speed according to signals from:
Coolant temperature sensors;
Hydraulic oil temperature sensors.
During Cold Start:
The fan runs at lower speed to:
Reduce unnecessary power consumption;
Lower noise levels;
Help the engine warm up faster.
During Heavy Loads and High Temperatures:
The fan automatically increases speed to provide maximum cooling airflow.
Reversible Fan System
A very practical option available on many skid steer loaders is the reversible cooling fan.
The fan periodically changes rotation direction, allowing it to blow accumulated debris out of the cooling fins.
This feature is especially useful in dusty environments or applications involving:
Agriculture;
Forestry;
Landscaping;
Recycling operations.
By automatically removing dust and debris buildup, a reversible fan helps maintain airflow, improves cooling efficiency, and reduces the frequency of manual cleaning.
