Why does the engine fan surge?

If the engine speed is not changing as an effect of the fan engaging, I'm not sure what the supposed concern is. The fan will come on and change speed as needed to cope with engine temperature as well as the use of air conditioning and ventilation systems. If you feel there is a concern, definitely have it checked locally at a shop near you where you can at least get an opinion in person on the matter. www.repairpal.com/repair-shops