More About Engine Fans

A word about installation: It is possible to install an engine fan backwards.
Contrary to popular belief, a fan installed backwards does not move air in the opposite direction.
That is, if a correctly installed fan draws air through the radiator, an incorrectly installed fan still draws air through the radiator it does not blow air through the radiator.


Here is a picture of a fan correctly installed on its drive.
You may be able to visualize that as the blades nearest to you rotate downward,
they draw air from left to right.


Here is a picture of the
same fan installed backwards.
You can see the blades are still positioned
to draw air from left to right in this photo.
You can also see how the shape of the blades
is very different from the picture above.

Why worry about which way the fan is installed?
An incorrectly installed fan draws air much less efficiently and will move significantly less volume. Engineers put a lot of time into the design and contour of the blades to produce maximum air movement. But when installed backwards, the shape of the blades is very poor for moving air.
If you are experiencing an over-heating problem, one of the things to check is that the fan is not installed backwards.

To make things easier, some fans have a painted message as shown here: