Engine Cooling System: NVH Dodge Pickup R2500

NOISE

Note. It is normal for fan noise to be louder (roaring) when

1. The underhood temperature is above the engagement point for the viscous drive coupling. This may occur when ambient (outside air temperature) is very high.
2. Engine loads and temperatures are high (such as when towing a trailer).
3. Cool silicone fluid within the fan drive unit is being redistributed back to its normal disengaged (warm) position. This can occur during the first 15 seconds to one minute after engine start-up on a cold engine.

Note. It is normal for fan noise to be louder (roaring) when

1. Fan duty cycle high. This may occur when ambient (outside air temperature) is very high.
2. Engine loads and temperatures are high such as when towing a trailer.
3. Cool silicone fluid within the fan drive unit is being redistributed back to its normal disengaged (warm) position. This can occur during the first 15 seconds to one minute after engine start-up on a cold engine.