Fan Clutch

Symptoms of a Bad or Failing Fan Clutch

Turbo enthusiasts or even non-specialists are aware that the radiator of their vehicle depends on constant airflow to disperse coolant. Without an adequate amount of airflow, the air around the radiator becomes stagnant and overheats, which prevents it from cooling the engine. Fan clutches are a critical component of this cooling system and control the operation of an engine cooling fan by transferring energy from the engine fan belt to the fan and allows it to turn at a certain speed, ultimately cooling the engine. 

While many newer vehicles use electric cooling fans to keep the engine cool, many older cars still use a mechanical fan clutch to control the fans. The fan clutch is a thermostatic device, which means its operation is based on temperature and is usually mounted on the water pump or another belt-driven fan pulley. 

The fan clutch spins loosely until the temperature reaches a certain level, then it fully engages so that the fan works at maximum efficiency. As the fan clutch is a cooling system component, any issues often cause overheating and other issues. 

How to Tell If Your Fan Clutch Is Going Bad?

The fan clutch is the most important component of the cooling system. A properly-functioning fan clutch is critical to the proper functioning of your engine, as it works to maintain a safe temperature range. 

If the fan clutch is failing, there are a couple of ways you may notice. Usually, a faulty fan clutch produces a few symptoms that can alert the driver of a potential issue. Understanding the symptoms of a bad or failing fan clutch is important as it’ll help you to prevent the risk of potential damage to the engine. 

A bad or failing fan clutch could also leave you stranded with expensive repair bills, so pay attention to the symptoms mentioned below as they will tell you if your fan clutch is going bad or failing:

  • Vehicle overheating

An overheating engine is often the first symptom that is commonly associated with a bad or failing fan clutch. Most drivers recognize when their engine overheats, but most don’t immediately think the fan clutch is the cause. 

The fan clutch controls the operation of the cooling fan, and if a fan clutch goes bad, it may not engage properly or at all. As a result, it will disable the fans or prevent them from working at maximum efficiency, which will lead to the engine overheating and more severe issues if left unattended. 

Another common problem caused by the opposite fan clutch failure is insufficient heat in winter. When the fan clutch seizes, it remains engaged all the time, cooling off the engine too much.

  1. Loose and Wobbling Fan

A fan clutch that is going bad may cause the engine fan to become loose and wobbly. Sometimes the wobbling of the fan can be heard while driving, especially at high speeds, such as on the freeway. To check if the fan is loose, turn on the engine while the car is parked, open the hood and check if the fan is wobbling while it spins. Another sign that shows if the engine fan is loose is oil coming out from the clutch hub.


  1. Excessively loud cooling fans

Another common symptom of a bad or failing fan clutch is excessively loud cooling fans. If the fan clutch gets stuck in the engaged position (which is not uncommon), it causes the fans to fully engage even when it is not suitable for them to function. Sometimes, this can result in an excessively loud engine from the fan blowing at full speed. The sound may be present at all times and easily audible when the engine is cold & hot.

  1. A decrease in acceleration, power & fuel efficiency

A decrease in performance is yet another symptom of a faulty fan clutch. A bad or failing fan clutch leaves the fan permanently engaged, causing a noisy engine and a decrease in performance. More importantly, a stuck fan clutch can cause excessive, unnecessary drag on the engine, which results in a drop in acceleration, power & fuel efficiency, sometimes to a quite noticeable degree.

How to Check the Fan Clutch?

There are a bunch of things you can do to check the fan clutch when the engine is off:

  • Spin the fan – Electronic types of fan clutch might freewheel, but most fan clutches should spin with a little effort. If the fan spins more than 3 times, the chances are that you have a bad fan clutch, and if the fan doesn’t spin at all, the bearing may be seized.
  • Wiggle the fan – Try moving the fan forward & backward. If you feel it click or it wobbles more than a quarter-inch, this may indicate a worn bearing.
  • Inspect for leaks – The key to fan clutch function is its heavy silicone fluid or oil. Viscous properties of silicone oil allow for soft engagement to drive the fan, so if it leaks out, the clutch will weaken and eventually fail.
  • Check the fan speed – When the fan clutch engages, with an accompanying rush of air, it can be detected audibly. Ideally, as engine temperature increases, a thermal fan clutch will engage at a specific temperature, and torque-limiting fan clutches will disengage at certain engine speeds. 
  • Scan tool – Some basic knowledge of a scan tool, as well as electronic testing, might be required to diagnose electronic fan clutches along with the sensors used in determining fan engagement. If you don’t possess this kind of knowledge, we at Diesel Components, Inc. can help in repairing your fan clutch in no time.

The internal combustion in the engine generates a lot of heat, and the main task of the engine cooling system, including the fan clutch, is moderating it. A little heat is good, as it helps in improving performance, fuel vaporization, and fuel economy along with warming up the cabin in the winter.

On the other hand, too much heat may pose a big problem, as it can render lubricating oil useless and melt non-metal engine parts. Also, an overheating engine could weld itself into scrap metal.

Now you know that the fan clutch is one of the primary cooling system components and is imperative to the proper operation of the engine. When it fails, the engine is at risk of serious damage due to overheating. If your fan clutch is bad or failed, replace it as soon as possible to prevent engine damage. 

If your vehicle displays any of the symptoms above, or you suspect that your fan clutch may have an issue, have the vehicle inspected by our professional technician at Diesel Components, Inc.  We will help you to determine if your vehicle needs a fan clutch replacement or repair. 

When it comes to fan clutch repair, technicians at Diesel Components, Inc. possess over 40 years of hands-on experience and training. They are highly skilled in using the most up-to-date fan clutch repair techniques. 


No matter what your application is as Diesel Components, Inc. can work on all popular models of fan clutches. If you have agricultural equipment, construction equipment, school or transit bus, on or off-highway vehicles, stationary engines, marine engines, or emergency response vehicles, you can contact Diesel Components, Inc. for all your fan clutch repair needs.