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Radiator Fan While under the hood spraying water repellent, check to see what type of radiator fan is fitted. Most 4x4's these days have the viscous coupling type, which means that when the engine is cool enough the fan doesn't spin at full speed. With the engine off, try and turn the fan. If it turns easily, you will probably get away without having to take off the fan belt. If it doesn't turn easily or yours is the fixed type, then you should remove the fan belt, If you don't and water enters the engine bay, the fan may act as a propeller, bend forward and cut a nice round hole through your radiator. It's certainly one problem you don't want to discover once you have completed the crossing. Even if it doesn't affect your radiator, you still do not want water being sprayed around, especially in a petrol 4x4.