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. In other words, 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.
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You may be able to visualize that as the blades nearest to you rotate downward, they are positioned at an angle to draw air from left to right in this photo. |
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same fan installed backwards. You can see the blades are still positioned at an angle to draw air from left to right in this photo. You can also see how the shape of the blades is very different from above. |
So why be concerned 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:
