How Do Cooling Fans Work?
A cooling fan works by drawing air through the fins of the radiator. To help illustrate how this works, think how warm you get when sitting in your vehicle with the windows up and without the A/C turned on. Then turn on your vehicle’s A/C or roll down the windows at speed and feel the incoming air. That incoming air helps to cool you down, and your vehicle’s cooling fan works the same way. When sitting in traffic the radiator fan, or cooling fan, draws air through the radiator to cool the fluid in the radiator, which in turn, cools the engine. When at speed, many electric fans shut off, whereas mechanical fans and fan clutch arrangements continue to turn to aid in cooling.
How Much Horsepower Does A Mechanical or Flex Fan Take from Your Hot Rod?
What we are talking about here is known as parasitic loss. This is the loss associated with how much horsepower is lost between the crank and the drive wheels via the engine’s accessory drive system, transmission, driveshaft, and differential. With a direct-drive radiator fan or fan clutch arrangement, the engine must turn that fan, as well. With an electric fan for cars, the engine is not working to turn the fan, which frees up horsepower otherwise soaked up by the fan. Typically, an electrical fan can free up to 10 horsepower otherwise being soaked up by a mechanical fan or flex fan.
At What Temperature Should Cooling Fans Cycle On?
This one has a couple different answers. With a direct-drive radiator fan, the fan is always on. With a fan clutch arrangement, the clutch decides when to engage and act like a direct-drive unit. At lower temperature, most fan clutches are not engaged, so it is freewheeling. With an electric fan arrangement, the fan will cycle on at a predetermined temperature, and cycle off at a predetermined temperature. These cycle-on and cycle-off temperatures are either preset by the temperature sensor/probe on/off range, or in some applications may be adjustable via the fan controller.
How Important Are Radiator Fan Shrouds?
Utilizing a radiator fan shroud with your cooling fan is very important. A radiator fan shroud attaches to the back of the radiator to direct air through the radiator. With a radiator fan shroud all incoming air is directed through the full core of the radiator for maximum efficiency and thermal transfer. Without a shroud of some sort the radiator cooling fan, be in mechanical or electric, will only pull air through the surface directly in front of the electric fan’s blade circumference. It becomes even less efficient running a belt driven fan without a shroud since the fan is often too far from the radiator core’s surface to effectively pull air through the core, which is why a shroud is even more imperative with mechanical fans Even if the radiator you purchase does not have a fan shroud, you can find a fan shroud universal to many radiator applications.
Do Cooling Fans Push or Pull Air?
The short answer to this question is yes. The long answer is you can have both, so let us explain. Most conventional cooling fans pull air through the radiator, but pusher fans also have their place. In many instances where a mechanical fan or even a fan clutch arrangement does not get the job done, a pusher fan works like a supercharger to force air through the radiator to aid cooling. Forcing air through the radiator helps to cool many combinations that need just a little help in running at a cooler temperature. That said, most electric fans are more efficient at pulling air rather than pushing air through a radiator core. Properly sizing your fan, using a shroud, and quality cooling components will usually keep your temp gauge in check.
How Do I Know If My Cooling Fan Is Not Working?
The easiest way to tell if your vehicle’s cooling fan, or fans, are not working, especially with an electric fan is the fan not cycling on. You could have a seized fan motor, failed sensor/controller, or wiring issue. With a cooling fan utilizing a fan clutch, if you can freely turn the fan when the engine is warm, that means the fan clutch is no longer doing its job and the fan clutch needs replacing. Many older vehicles have a direct drive cooling fan, and with those, if the fan is moving and you still have overheating issues, your cooling system has other concerns or your shroud is missing, damaged, or the fan spacer is incorrect for your application (the fan should be halfway into the shroud to properly pull air through the radiator core). In all cases, though, your vehicle’s cooling system may not be capable of keeping up with your engine’s needs. An upgraded cooling system may be in order.
Another way of knowing your cooling fan is not working is if your vehicle overheats. If that is the case, the radiator fan, or cooling fan could be the issue. However, with a cooling system, it could be anything from a bad thermostat or clogged radiator or hoses, to a blown head gasket. Overly advanced ignition timing and too lean of a fuel system are other aspects that can cause high engine temperatures and overheating, even though the radiator fan is working.
