Stay Ahead of Disaster: A Complete Guide To Preventing Failing Fan Clutches

Understand the important role your fan clutch plays in your heavy duty engine cooling system and the reasons for their failure. Learn symptoms to watch for and ways to test your fan clutch for upcoming failure before it happens.

Understanding the operation and importance of your fan clutch can help you stay ahead of disaster and save you from unforeseen downtime. The fan clutch is an important component in your truck’s engine cooling system. Fan clutches help to manage the cooling needs and at the same time help manage engine power demands by utilizing their function only when called for. This results in better engine efficiency and lowering fuel costs.

In this article, we will discuss the operation of Air Fan Clutches, common causes of failure, symptoms to watch for, and things that can be done to maintain this component.

  1. How Do Fan Clutches Work?
  2. Causes For Fan Clutch Failure
  3. Fan Clutch Symptoms To Watch For
  4. Servicing and Maintaining Your Fan Clutch
  5. Wheelco’s Fan Clutch Recommendation

How Do Fan Clutches Work?​

As your truck is being used, the engine will naturally heat up in temperature. Any time your engine cooling system is operating in the normal range, the fan clutch is not engaged and is simply freewheeling, thus not creating an unnecessary power load. As the temperature continues to rise, the trucks temperature monitoring system tracks the temperature. This is done by an electrical temperature sensor in the engine’s water jacket. When the temperature exceeds the manufacturers recommended temperature range, a signal is sent to the electric/air solenoid, which, depending on if it is wired normally open or closed, will then supply air or cut off the air supply to the fan clutch. Dependent on your fan clutch type, either air fan clutch or viscous fan clutch, the fan clutch’s spring pressure locks and engages the fan clutch to drive. The demand and frequency of these cycles is dictated by driving application demands as well as ambient temperatures in your operating region.

Causes For Fan Clutch Failure​

Fan clutches will fail over time from repetitive use. While there is no specific lifespan for a fan clutch, always keep your eyes and ears open for issues with your fan clutch. Fan clutches that fail can be caused by a few different reasons, but the two most common reasons for fan clutch failure include the following.

  • High Torque Demand
  • Bearing Failure

High Torque Demand​

Torque is generated primarily by the fan blade itself when locked up and driving. Earlier fan blade & fan clutch configurations dealt with fan clutch torque ratings of approximately 2,100 in/lbs. As engines and cooling demands increased through the years, the torque demands grew to as much as 2800 in/lbs. The main contributor was the fan blades necessary to generate acceptable cooling for the system.

Fan blade changes ranged in their newer designs to include larger diameter, number of blades, and steeper blade pitches. These design changes increased the overall RPM of the blade itself and the torque required of the fan clutch. As these torque demands increased, the OE fan clutch manufacturers made changes with heavier springs and various designs in the support bearings in order to meet the higher fan loads. As torque demands approached 2800 in/lbs, OE fan clutch manufacturers have been successful in moving their clutch ratings to approximately 2400 in/lbs.

With the bigger design fan blades, the fan blades want to pull themselves away from the fan clutch, much like an airplane pulls itself through the air. This, in turn pulls the lining apart against the spring pressure and causes the friction to slip. The result is high internal heat causing linings to get worn down and bearings fail.

Bearing Failure​

Bearing failure is a very common failure, and largely a result of torque as noted above. Once the fan clutch starts to rotate the fan blade, the RPMs will increase and create a thrust behind the fan blade. This thrust pulls the fan blade away from the fan clutch, increasing the amount of torque applied to the fan clutch. Over time, this creates more fan clutch slippage and causes high internal heat that will break down your bearings prematurely. Multiple bearing design enhancements have been utilized by fan clutch OEM’s to better withstand the torque demands and improve lifespan of the fan clutch.

Fan Clutch Symptoms To Watch For​

By knowing the symptoms of a failing fan clutch, you can stay ahead and save yourself from unforeseen downtime. Using your eyes, ears, and nose can prevent you from being stuck along the road in the middle of nowhere. Watch, listen, and smell for these symptoms of your fan clutch going bad.

  • Overheating
  • Decrease in Fuel Mileage
  • Loud Fan Running Noise
  • Burning Smell

Servicing & Maintaining Your Fan Clutch​

The following recommended service maintenance guidelines are the key to extending your fan clutch’s life and preventing failures on the road.

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Every 10,000 miles​

Check for air leaks around the clutch air chamber, check sentry fuse (if equipped), check for leaks on the air inlet ports, air hoses, and around connections at the solenoid valve. If leaks persist in the fan clutch body itself, replace the fan clutch seals as corrective maintenance.

Every 25,000 miles​

In addition to performing items listed in the 10,000 miles maintenance, visually inspect the fan clutch housing and around the piston friction disc for signs of discoloration or overheating. Overheating is the result of the clutch slipping and this is almost always due to low air pressure in the clutch. This can be caused by low system air pressure or an air leak in the system, or in the clutch itself. The fan clutch needs a minimum of 90 PSI air pressure to function properly. Repair any leaks as needed.

Also, check for worn sheave bearings. This is done by removing the drive belts and rotating the sheave by hand to detect any resistance or roughness. Then check for worn hub bearings by manually rotating the fan blade. Both of these should rotate freely.

Next inspect and measure the thickness of the friction to ensure that it is within minimum specifications. Replace worn linings as a corrective measure.

In addition, check electrical wiring and connectors and replace or repair as may be needed.

Finally, with a minimum or 90 PSI air pressure, manually activate the clutch to see that its engaging and disengaging properly.

Wheelco’s Fan Clutch Recommendation​

At Wheelco, we stand apart from competitors by offering only the most innovative aftermarket products. We carry some of the highest quality and advanced fan clutches and clutch rebuild kits on the market to give you peace of mind for years to come. Wheelco Truck & Trailer proudly carries Kit Masters  fan clutch products for your engine cooling system needs.

With Kit Masters GoldTop fan clutch rebuild kits offering over 5,000 inch-pounds of torque, you can rest assure your fan clutch will be able to produce enough torque for nearly all fan blades. Kit Masters pairs that enormous amount of torque with their patented “fail safe” Auto Lock technology. This feature ensures that your fan clutch remains in the lock up position in the event of lining or slippage failure. Your fan will stay engaged until you’re able to safely return home, or to your preferred maintenance shop, to replace your fan clutch. No more towing bill, out of town shop rates, unapproved parts installed, and most importantly, no more downtime.

Visit with our Wheelco team of aftermarket experts and service techs to help find the fan clutch that meets and exceeds your needs. Give us a calltext, or message us through chat to get started, or stop in to one of our stores today.

About Wheelco Truck & Trailer

At Wheelcobeing customer driven is more than just a motto we live by. It means that our employees will do everything we can to best serve you, our valued customer.

Customer driven is more than just offering you advice, giving time-honored service or contributing the latest tech-support. It’s about being there—whenever and wherever you need us—in-person, over the phone or online.

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