Getting To Know Your Engine Cooling System: Fan Clutches

How Fan Clutches Control Your Semi-Truck Engine's Temperature

If you drive a truck, then you know how important it is to always keep your engine at a normal temperature. Without proper cooling, your semi-truck's engine will overheat and shut down. A great way to make sure your engine is cool at all times, a good fan clutch will help your truck operate as intended.
If you've wanted to know a little more about engine cooling, you've come to the right place. Our experts have prepared the following article on fan clutches to familiarize you with fan clutches. Read on to learn more about the fan clutch in your commercial vehicle!

What is a Fan Clutch?

A fan clutch is a mechanism that regulates the operation of the engine cooling fan, ensuring optimal cooling efficiency, and preventing overheating. It is a critical part of many semi-truck engines, serving as a safeguard against potential engine damage caused by excessive heat.

How Does a Fan Clutch Work?

The fundamental purpose of a fan clutch is to modulate the speed at which the engine cooling fan operates. When the engine is running, it generates heat, and this heat needs to be dissipated to prevent the engine from becoming too hot. The cooling fan assists in this process by drawing air through the radiator, which in turn helps to cool down the engine coolant.

A fan clutch engages and disengages the fan depending on the temperature of the engine. When the engine is running at a normal temperature, the fan clutch allows the fan to rotate at a slower speed. This reduces unnecessary power consumption. As the engine temperature rises, the fan clutch activates, causing the fan to spin faster. This higher rotational speed enhances the airflow through the radiator, resulting in more effective heat dissipation. 

What are the Parts of a Fan Clutch?

A fan clutch consists of several essential components that work together to regulate the fan's speed and contribute to efficient cooling. The core parts of a fan clutch include:

1.     Thermostat: The thermostat is a temperature-sensitive device that detects changes in engine temperature. It is responsible for engaging or disengaging of the fan clutch. When the engine temperature rises beyond a certain threshold, the thermostat signals the fan clutch to engage and increase the fan's rotational speed.

2.     Bimetallic Spring: The bimetallic spring reacts to changes in temperature by expanding or contracting. This expansion or contraction influences the position of the clutch plate, which in turn controls the engagement of the fan.

3.     Clutch Plate: The clutch plate is connected to the bimetallic spring. When the bimetallic spring expands or contracts, it causes the clutch plate to move. This movement alters the position of the fan blades, adjusting their angle and rotational speed accordingly.

4.     Fluid Filled Chamber: Inside the fan clutch, there is a fluid-filled chamber that regulates the fan's operation. The fluid is sensitive to temperature changes and helps control the movement of the clutch plate.

What Types of Fan Clutch are Available?

There are two main types of fan clutches: thermostatic and electric. Each type has its own advantages for different applications. Types of fan clutch include:

1.     Thermostatic Fan Clutches: These are the traditional and more common type of fan clutches. When the engine temperature rises, the thermostat detects the change and signals the fan clutch to engage, increasing the fan's speed. Once the engine cools down, the fan clutch disengages.

2.     Electric Fan Clutches: Electric fan clutches operate based on electrical signals rather than mechanical temperature sensing. These clutches are controlled by the vehicle's Engine Control Module (ECM) and can be adjusted more precisely. Electric fan clutches can vary the fan speed based on vehicle speed, air conditioning usage, and engine load. This flexibility can lead to improved fuel efficiency.

What are the Benefits of Fan Clutches?

The adaptation to efficient semi-truck engine cooling fan clutches presents several benefits to truck operators, manufacturers, and the environment. These benefits include:

1.     Fuel Efficiency: Fan clutches prevent excessive energy consumption, resulting in improved fuel efficiency and reduced operational costs for trucking companies.

2.     Extended Engine Life: Maintaining proper engine temperatures through effective cooling helps extend the lifespan of the engine and its components, reducing maintenance and replacement costs.

3.     Emission Reduction: Proper cooling contributes to cleaner exhaust emissions, aligning with environmental regulations.

4.     Enhanced Performance: Consistent engine temperatures ensure that the engine operates at its designed efficiency, translating to better overall performance and power output.

Fan Clutch Troubleshooting

A fan clutch requires 100 PSI (6.8 bars) for it to operate properly. When you're troubleshooting, you will want to look for any issue that can cause partial engagement. Sometimes, air leaking past the solenoid valve seals into the airline can create a build-up of pressure. If there is a pressure drop caused by partial disengagement, it could point to a bad solenoid, up-stream air leaks, airline blockage, air leaks from the body, or low air pressure.

You will also want to make sure you check your fan blades for proper clearance to the shroud, radiator, and other engine systems. Check for anything that may be obstructing the fan blade. It is also a good idea to check for splits or cracks in the fan blades that can cause the unit to run out of balance.

How Often Should I Check My Fan Clutch?

Routine inspections of your fan clutch should be performed once every 124,000 miles or so. Check to make sure the bearing rotation is smooth by removing and plugging the airlines at the fan clutch input, rotating the pump pulley, and loosening the fan belts. Also check for wear and tear of friction facing. The thickness of the friction facing should be approximately 4mm. If it isn't, drain the inline air-filter daily to release any moisture.

Read More About Engine Cooling Systems

If you would like to continue reading more about the engine cooling systems in your semi-truck, our experts have developed several articles you will want to look through.

·       Getting to Know Your Engine Cooling System

·       Getting to Know Your Engine Cooling System: Charge Air Coolers

·       Getting To Know Your Engine Cooling System: Cooling Tanks

·       Getting to Know Your Engine Cooling System: Fan Blades

·       Getting to Know Your Engine Cooling System: Oil Coolers

·       Getting To Know Your Engine Cooling System: Radiators

·       Getting to Know Your Engine Cooling System: Water Pumps

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