Introduction

A remarkably small and simple device, the fan spacer, if required on your motor vehicle is exceptionally important.

It is a small piece of metal, either solid or cast, which sits between the cooling fan and the fan pulley to correctly position the fan.

Application

To reduce production costs, many automotive parts are built the same, even though they may be used on different engine sizes, or even different vehicle models.

The fan - assuming it is not a powerful electric unit, but is powered by the fanbelt - needs to be at a pretty precise position relative to the radiator. It should be close enough to the radiator to ensure good airflow, but far enough that it doesn't foul the radiator fins, even when the fan blades flex slightly, as they do during normal operation.

Because many stock parts are used, the fan pulley and radiator may be situated different distances apart, and also, larger engines may have parts which could be hit by the rear of the fan, should it be situated too near the pulley.

Here the fan spacer comes in, and we look at the BMC Mini as an example. The traditional 850 and 998cc Mini are built so that the fan is in the correct place when attached directly to the pulley. However, along came the Clubman - with a larger engine bay. The radiator had moved 6mm away from the engine, and so the fan now needed to be closer to the radiator to give effective cooling - hence a 6mm spacer was introduced.

The 1275cc Mini has a larger engine, with parts on the back which will foul a fan with no spacer, but there is insufficient room before the radiator to move the fan out by 6mm, so a 3mm spacer was introduced.

Precision

One possible solution to the problem could be to build up a stack of washers between the fan and the pulley. This will space the fan correctly, but it should be noted that the spacer is a precision-machined part and it is balanced to avoid vibration.

A stack of washers could easily upset the balance, and cause vibration or worse - maybe breaking the fan at high rpm.

Problems

With an incorrect fan spacing, cooling will be inefficient, and damage may occur to the radiator, fan or other engine parts. It is not a problem which will suddenly occur, but may come up after service if a spacer has been omitted after stripping and rebuilding the cooling system.

The solution is to find out what spacer is required from expert advice, and simply obtain and fit the spacer. It is a simple job which requires removal of the radiator and fan, but can easily be accomplished in an hour.


Sources:
Yes, I sat in a field with my toolbox out and big bottles of coolant having forgotten to fit the spacer the day before a car show. The noise as the fan blades flew off was fantastic!

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